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Actinide

October 15, 2023

Actinides in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson

The actinide (/ˈæktɪnaɪd/) or actinoid (/ˈæktɪnɔɪd/) series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium. The actinide series derives its name from the first element in the series, actinium. The informal chemical symbol An is used in general discussions of actinide chemistry to refer to any actinide.[1][2][3]

The 1985 IUPAC Red Book recommends that actinoid be used rather than actinide, since the suffix -ide normally indicates a negative ion. However, owing to widespread current use, actinide is still allowed. Since actinoid literally means actinium-like (cf. humanoid or android), it has been argued for semantic reasons that actinium cannot logically be an actinoid, but IUPAC acknowledges its inclusion based on common usage.[4]

All the actinides are f-block elements, except the final one (lawrencium) which is a d-block element:[5][6] on this basis the inclusion of lawrencium among the actinides has sometimes been questioned,[7] as it is also a transition metal. The series mostly corresponds to the filling of the 5f electron shell, although in the ground state many have anomalous configurations involving the filling of the 6d shell due to interelectronic repulsion. In comparison with the lanthanides, also mostly f-block elements, the actinides show much more variable valence. They all have very large atomic and ionic radii and exhibit an unusually large range of physical properties. While actinium and the late actinides (from americium onwards) behave similarly to the lanthanides, the elements thorium, protactinium, and uranium are much more similar to transition metals in their chemistry, with neptunium and plutonium occupying an intermediate position.

All actinides are radioactive and release energy upon radioactive decay; naturally occurring uranium and thorium, and synthetically produced plutonium are the most abundant actinides on Earth. These are used in nuclear reactors and nuclear weapons. Uranium and thorium also have diverse current or historical uses, and americium is used in the ionization chambers of most modern smoke detectors.

Of the actinides, primordial thorium and uranium occur naturally in substantial quantities. The radioactive decay of uranium produces transient amounts of actinium and protactinium, and atoms of neptunium and plutonium are occasionally produced from transmutation reactions in uranium ores. The other actinides are purely synthetic elements.[1][8] Nuclear weapons tests have released at least six actinides heavier than plutonium into the environment; analysis of debris from a 1952 hydrogen bomb explosion showed the presence of americium, curium, berkelium, californium, einsteinium and fermium.[9]

In presentations of the periodic table, the f-block elements are customarily shown as two additional rows below the main body of the table.[1] This convention is entirely a matter of aesthetics and formatting practicality; a rarely used wide-formatted periodic table inserts the 4f and 5f series in their proper places, as parts of the table's sixth and seventh rows (periods).

Discovery, isolation and synthesis Edit

Synthesis of transuranium elements[10][notes 1]
Element Year Method
Neptunium 1940 Bombarding 238U by neutrons
Plutonium 1941 Bombarding 238U by deuterons
Americium 1944 Bombarding 239Pu by neutrons
Curium 1944 Bombarding 239Pu by α-particles
Berkelium 1949 Bombarding 241Am by α-particles
Californium 1950 Bombarding 242Cm by α-particles
Einsteinium 1952 As a product of nuclear explosion
Fermium 1952 As a product of nuclear explosion
Mendelevium 1955 Bombarding 253Es by α-particles
Nobelium 1965 Bombarding 243Am by 15N
or 238U with 22Ne
Lawrencium 1961
–1971 		Bombarding 252Cf by 10B or 11B
and of 243Am with 18O

Like the lanthanides, the actinides form a family of elements with similar properties. Within the actinides, there are two overlapping groups: transuranium elements, which follow uranium in the periodic table; and transplutonium elements, which follow plutonium. Compared to the lanthanides, which (except for promethium) are found in nature in appreciable quantities, most actinides are rare. Most do not occur in nature, and of those that do, only thorium and uranium do so in more than trace quantities. The most abundant or easily synthesized actinides are uranium and thorium, followed by plutonium, americium, actinium, protactinium, neptunium, and curium.[11]

The existence of transuranium elements was suggested in 1934 by Enrico Fermi, based on his experiments.[12][13] However, even though four actinides were known by that time, it was not yet understood that they formed a family similar to lanthanides. The prevailing view that dominated early research into transuranics was that they were regular elements in the 7th period, with thorium, protactinium and uranium corresponding to 6th-period hafnium, tantalum and tungsten, respectively. Synthesis of transuranics gradually undermined this point of view. By 1944, an observation that curium failed to exhibit oxidation states above 4 (whereas its supposed 6th period homolog, platinum, can reach oxidation state of 6) prompted Glenn Seaborg to formulate an "actinide hypothesis". Studies of known actinides and discoveries of further transuranic elements provided more data in support of this position, but the phrase "actinide hypothesis" (the implication being that a "hypothesis" is something that has not been decisively proven) remained in active use by scientists through the late 1950s.[14][15]

At present, there are two major methods of producing isotopes of transplutonium elements: (1) irradiation of the lighter elements with neutrons; (2) irradiation with accelerated charged particles. The first method is more important for applications, as only neutron irradiation using nuclear reactors allows the production of sizeable amounts of synthetic actinides; however, it is limited to relatively light elements. The advantage of the second method is that elements heavier than plutonium, as well as neutron-deficient isotopes, can be obtained, which are not formed during neutron irradiation.[16]

In 1962–1966, there were attempts in the United States to produce transplutonium isotopes using a series of six underground nuclear explosions. Small samples of rock were extracted from the blast area immediately after the test to study the explosion products, but no isotopes with mass number greater than 257 could be detected, despite predictions that such isotopes would have relatively long half-lives of α-decay. This non-observation was attributed to spontaneous fission owing to the large speed of the products and to other decay channels, such as neutron emission and nuclear fission.[17]

From actinium to uranium Edit

 
Enrico Fermi suggested the existence of transuranium elements in 1934.

Uranium and thorium were the first actinides discovered. Uranium was identified in 1789 by the German chemist Martin Heinrich Klaproth in pitchblende ore. He named it after the planet Uranus,[8] which had been discovered eight years earlier. Klaproth was able to precipitate a yellow compound (likely sodium diuranate) by dissolving pitchblende in nitric acid and neutralizing the solution with sodium hydroxide. He then reduced the obtained yellow powder with charcoal, and extracted a black substance that he mistook for metal.[18] Sixty years later, the French scientist Eugène-Melchior Péligot identified it as uranium oxide. He also isolated the first sample of uranium metal by heating uranium tetrachloride with metallic potassium.[19] The atomic mass of uranium was then calculated as 120, but Dmitri Mendeleev in 1872 corrected it to 240 using his periodicity laws. This value was confirmed experimentally in 1882 by K. Zimmerman.[20][21]

Thorium oxide was discovered by Friedrich Wöhler in the mineral thorianite, which was found in Norway (1827).[22] Jöns Jacob Berzelius characterized this material in more detail in 1828. By reduction of thorium tetrachloride with potassium, he isolated the metal and named it thorium after the Norse god of thunder and lightning Thor.[23][24] The same isolation method was later used by Péligot for uranium.[8]

Actinium was discovered in 1899 by André-Louis Debierne, an assistant of Marie Curie, in the pitchblende waste left after removal of radium and polonium. He described the substance (in 1899) as similar to titanium[25] and (in 1900) as similar to thorium.[26] The discovery of actinium by Debierne was however questioned in 1971[27] and 2000,[28] arguing that Debierne's publications in 1904 contradicted his earlier work of 1899–1900. This view instead credits the 1902 work of Friedrich Oskar Giesel, who discovered a radioactive element named emanium that behaved similarly to lanthanum. The name actinium comes from the Ancient Greek: ακτίς, ακτίνος (aktis, aktinos), meaning beam or ray. This metal was discovered not by its own radiation but by the radiation of the daughter products.[29][30] Owing to the close similarity of actinium and lanthanum and low abundance, pure actinium could only be produced in 1950. The term actinide was probably introduced by Victor Goldschmidt in 1937.[31][32]

Protactinium was possibly isolated in 1900 by William Crookes.[33] It was first identified in 1913, when Kasimir Fajans and Oswald Helmuth Göhring encountered the short-lived isotope 234mPa (half-life 1.17 minutes) during their studies of the 238U decay. They named the new element brevium (from Latin brevis meaning brief);[34][35] the name was changed to protoactinium (from Greek πρῶτος + ἀκτίς meaning "first beam element") in 1918 when two groups of scientists, led by the Austrian Lise Meitner and Otto Hahn of Germany and Frederick Soddy and John Cranston of Great Britain, independently discovered the much longer-lived 231Pa. The name was shortened to protactinium in 1949. This element was little characterized until 1960, when A. G. Maddock and his co-workers in the U.K. isolated 130 grams of protactinium from 60 tonnes of waste left after extraction of uranium from its ore.[36]

Neptunium and above Edit

Neptunium (named for the planet Neptune, the next planet out from Uranus, after which uranium was named) was discovered by Edwin McMillan and Philip H. Abelson in 1940 in Berkeley, California.[37] They produced the 239Np isotope (half-life = 2.4 days) by bombarding uranium with slow neutrons.[36] It was the first transuranium element produced synthetically.[38]

 
Glenn T. Seaborg and his group at the University of California at Berkeley synthesized Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No and element 106, which was later named seaborgium in his honor while he was still living. They also synthesized more than a hundred actinide isotopes.

Transuranium elements do not occur in sizeable quantities in nature and are commonly synthesized via nuclear reactions conducted with nuclear reactors. For example, under irradiation with reactor neutrons, uranium-238 partially converts to plutonium-239:

 

This synthesis reaction was used by Fermi and his collaborators in their design of the reactors located at the Hanford Site, which produced significant amounts of plutonium-239 for the nuclear weapons of the Manhattan Project and the United States' post-war nuclear arsenal.[39]

Actinides with the highest mass numbers are synthesized by bombarding uranium, plutonium, curium and californium with ions of nitrogen, oxygen, carbon, neon or boron in a particle accelerator. Thus nobelium was produced by bombarding uranium-238 with neon-22 as

 .

The first isotopes of transplutonium elements, americium-241 and curium-242, were synthesized in 1944 by Glenn T. Seaborg, Ralph A. James and Albert Ghiorso.[40] Curium-242 was obtained by bombarding plutonium-239 with 32-MeV α-particles

 .

The americium-241 and curium-242 isotopes also were produced by irradiating plutonium in a nuclear reactor. The latter element was named after Marie Curie and her husband Pierre who are noted for discovering radium and for their work in radioactivity.[41]

Bombarding curium-242 with α-particles resulted in an isotope of californium 245Cf (1950), and a similar procedure yielded in 1949 berkelium-243 from americium-241.[42] The new elements were named after Berkeley, California, by analogy with its lanthanide homologue terbium, which was named after the village of Ytterby in Sweden.[43]

In 1945, B. B. Cunningham obtained the first bulk chemical compound of a transplutonium element, namely americium hydroxide.[44] Over the few years, milligram quantities of americium and microgram amounts of curium were accumulated that allowed production of isotopes of berkelium (Thomson, 1949)[45][46] and californium (Thomson, 1950).[47][48][49] Sizeable amounts of these elements were produced in 1958 (Burris B. Cunningham and Stanley G. Thomson),[50] and the first californium compound (0.3 µg of CfOCl) was obtained in 1960 by B. B. Cunningham and J. C. Wallmann.[51]

Einsteinium and fermium were identified in 1952–1953 in the fallout from the "Ivy Mike" nuclear test (1 November 1952), the first successful test of a hydrogen bomb. Instantaneous exposure of uranium-238 to a large neutron flux resulting from the explosion produced heavy isotopes of uranium, including uranium-253 and uranium-255, and their β-decay yielded einsteinium-253 and fermium-255. The discovery of the new elements and the new data on neutron capture were initially kept secret on the orders of the US military until 1955 due to Cold War tensions.[9][52] Nevertheless, the Berkeley team were able to prepare einsteinium and fermium by civilian means, through the neutron bombardment of plutonium-239, and published this work in 1954 with the disclaimer that it was not the first studies that had been carried out on those elements.[53][54] The "Ivy Mike" studies were declassified and published in 1955.[52] The first significant (submicrograms) amounts of einsteinium were produced in 1961 by Cunningham and colleagues, but this has not been done for fermium yet.[55]

The first isotope of mendelevium, 256Md (half-life 87 min), was synthesized by Albert Ghiorso, Glenn T. Seaborg, Gregory R. Choppin, Bernard G. Harvey and Stanley G. Thompson when they bombarded an 253Es target with alpha particles in the 60-inch cyclotron of Berkeley Radiation Laboratory; this was the first isotope of any element to be synthesized one atom at a time.[56]

There were several attempts to obtain isotopes of nobelium by Swedish (1957) and American (1958) groups, but the first reliable result was the synthesis of 256No by the Russian group (Georgy Flyorov et al.) in 1965, as acknowledged by the IUPAC in 1992. In their experiments, Flyorov et al. bombarded uranium-238 with neon-22.[10]

In 1961, Ghiorso et al. obtained the first isotope of lawrencium by irradiating californium (mostly californium-252) with boron-10 and boron-11 ions.[10] The mass number of this isotope was not clearly established (possibly 258 or 259) at the time. In 1965, 256Lr was synthesized by Flyorov et al. from 243Am and 18O. Thus IUPAC recognized the nuclear physics teams at Dubna and Berkeley as the co-discoverers of lawrencium.

Isotopes Edit

 
Actinides have 89–103 protons and usually 117–159 neutrons.

32 isotopes of actinium and eight excited isomeric states of some of its nuclides were identified by 2016.[57] Three isotopes, 225Ac, 227Ac and 228Ac, were found in nature and the others were produced in the laboratory; only the three natural isotopes are used in applications. Actinium-225 is a member of the radioactive neptunium series;[60] it was first discovered in 1947 as a decay product of uranium-233, it is an α-emitter with a half-life of 10 days. Actinium-225 is less available than actinium-228, but is more promising in radiotracer applications.[30] Actinium-227 (half-life 21.77 years) occurs in all uranium ores, but in small quantities. One gram of uranium (in radioactive equilibrium) contains only 2×10−10 gram of 227Ac.[30][57] Actinium-228 is a member of the radioactive thorium series formed by the decay of 228Ra;[60] it is a β− emitter with a half-life of 6.15 hours. In one tonne of thorium there is 5×10−8 gram of 228Ac. It was discovered by Otto Hahn in 1906.[30]

There are 31 known isotopes of thorium ranging in mass number from 208 to 238.[57] Of these, the longest-lived is 232Th, whose half-life of 1.4×1010 years means that it still exists in nature as a primordial nuclide. The next longest-lived is 230Th, an intermediate decay product of 238U with a half-life of 75,400 years. Several other thorium isotopes have half-lives over a day; all of these are also transient in the decay chains of 232Th, 235U, and 238U.

28 isotopes of protactinium are known with mass numbers 212–239[57] as well as three excited isomeric states. Only 231Pa and 234Pa have been found in nature. All the isotopes have short lifetimes, except for protactinium-231 (half-life 32,760 years). The most important isotopes are 231Pa and 233Pa, which is an intermediate product in obtaining uranium-233 and is the most affordable among artificial isotopes of protactinium. 233Pa has convenient half-life and energy of γ-radiation, and thus was used in most studies of protactinium chemistry. Protactinium-233 is a β-emitter with a half-life of 26.97 days.[57][61]

There are 26 known isotopes of uranium, having mass numbers 215–242 (except 220 and 241).[58] Three of them, 234U, 235U and 238U, are present in appreciable quantities in nature. Among others, the most important is 233U, which is a final product of transformation of 232Th irradiated by slow neutrons. 233U has a much higher fission efficiency by low-energy (thermal) neutrons, compared e.g. with 235U. Most uranium chemistry studies were carried out on uranium-238 owing to its long half-life of 4.4×109 years.[62]

There are 24 isotopes of neptunium with mass numbers of 219, 220, and 223–244;[58] they are all highly radioactive. The most popular among scientists are long-lived 237Np (t1/2 = 2.20×106 years) and short-lived 239Np, 238Np (t1/2 ~ 2 days).[38]

There are 20 known isotopes of plutonium, having mass numbers 228–247.[58] The most stable isotope of plutonium is 244Pu with half-life of 8.13×107 years.[63]

Eighteen isotopes of americium are known with mass numbers from 229 to 247 (with the exception of 231).[58] The most important are 241Am and 243Am, which are alpha-emitters and also emit soft, but intense γ-rays; both of them can be obtained in an isotopically pure form. Chemical properties of americium were first studied with 241Am, but later shifted to 243Am, which is almost 20 times less radioactive. The disadvantage of 243Am is production of the short-lived daughter isotope 239Np, which has to be considered in the data analysis.[64]

Among 19 isotopes of curium, ranging in mass number from 233 to 251,[58] the most accessible are 242Cm and 244Cm; they are α-emitters, but with much shorter lifetime than the americium isotopes. These isotopes emit almost no γ-radiation, but undergo spontaneous fission with the associated emission of neutrons. More long-lived isotopes of curium (245–248Cm, all α-emitters) are formed as a mixture during neutron irradiation of plutonium or americium. Upon short irradiation, this mixture is dominated by 246Cm, and then 248Cm begins to accumulate. Both of these isotopes, especially 248Cm, have a longer half-life (3.48×105 years) and are much more convenient for carrying out chemical research than 242Cm and 244Cm, but they also have a rather high rate of spontaneous fission. 247Cm has the longest lifetime among isotopes of curium (1.56×107 years), but is not formed in large quantities because of the strong fission induced by thermal neutrons.

Seventeen isotopes of berkelium were identified with mass numbers 233–234, 236, 238, and 240–252.[58] Only 249Bk is available in large quantities; it has a relatively short half-life of 330 days and emits mostly soft β-particles, which are inconvenient for detection. Its alpha radiation is rather weak (1.45×10−3% with respect to β-radiation), but is sometimes used to detect this isotope. 247Bk is an alpha-emitter with a long half-life of 1,380 years, but it is hard to obtain in appreciable quantities; it is not formed upon neutron irradiation of plutonium because of the β-stability of isotopes of curium isotopes with mass number below 248.[64]

The 20 isotopes of californium with mass numbers 237–256 are formed in nuclear reactors;[58] californium-253 is a β-emitter and the rest are α-emitters. The isotopes with even mass numbers (250Cf, 252Cf and 254Cf) have a high rate of spontaneous fission, especially 254Cf of which 99.7% decays by spontaneous fission. Californium-249 has a relatively long half-life (352 years), weak spontaneous fission and strong γ-emission that facilitates its identification. 249Cf is not formed in large quantities in a nuclear reactor because of the slow β-decay of the parent isotope 249Bk and a large cross section of interaction with neutrons, but it can be accumulated in the isotopically pure form as the β-decay product of (pre-selected) 249Bk. Californium produced by reactor-irradiation of plutonium mostly consists of 250Cf and 252Cf, the latter being predominant for large neutron fluences, and its study is hindered by the strong neutron radiation.[65]

Properties of some transplutonium isotope pairs[66]
Parent
isotope 		t1/2 Daughter
isotope 		t1/2 Time to establish
radioactive equilibrium
243Am 7370 years 239Np 2.35 days 47.3 days
245Cm 8265 years 241Pu 14 years 129 years
247Cm 1.64×107 years 243Pu 4.95 hours 7.2 days
254Es 270 days 250Bk 3.2 hours 35.2 hours
255Es 39.8 days 255Fm 22 hours 5 days
257Fm 79 days 253Cf 17.6 days 49 days

Among the 18 known isotopes of einsteinium with mass numbers from 240 to 257,[58] the most affordable is 253Es. It is an α-emitter with a half-life of 20.47 days, a relatively weak γ-emission and small spontaneous fission rate as compared with the isotopes of californium. Prolonged neutron irradiation also produces a long-lived isotope 254Es (t1/2 = 275.5 days).[65]

Twenty isotopes of fermium are known with mass numbers of 241–260. 254Fm, 255Fm and 256Fm are α-emitters with a short half-life (hours), which can be isolated in significant amounts. 257Fm (t1/2 = 100 days) can accumulate upon prolonged and strong irradiation. All these isotopes are characterized by high rates of spontaneous fission.[65][67]

Among the 17 known isotopes of mendelevium (mass numbers from 244 to 260),[58] the most studied is 256Md, which mainly decays through the electron capture (α-radiation is ≈10%) with the half-life of 77 minutes. Another alpha emitter, 258Md, has a half-life of 53 days. Both these isotopes are produced from rare einsteinium (253Es and 255Es respectively), that therefore limits their availability.[57]

Long-lived isotopes of nobelium and isotopes of lawrencium (and of heavier elements) have relatively short half-lives. For nobelium, 11 isotopes are known with mass numbers 250–260 and 262. The chemical properties of nobelium and lawrencium were studied with 255No (t1/2 = 3 min) and 256Lr (t1/2 = 35 s). The longest-lived nobelium isotope, 259No, has a half-life of approximately 1 hour.[57] Lawrencium has 13 known isotopes with mass numbers 251–262 and 266. The most stable of them all is 266Lr with a half life of 11 hours.

Among all of these, the only isotopes that occur in sufficient quantities in nature to be detected in anything more than traces and have a measurable contribution to the atomic weights of the actinides are the primordial 232Th, 235U, and 238U, and three long-lived decay products of natural uranium, 230Th, 231Pa, and 234U. Natural thorium consists of 0.02(2)% 230Th and 99.98(2)% 232Th; natural protactinium consists of 100% 231Pa; and natural uranium consists of 0.0054(5)% 234U, 0.7204(6)% 235U, and 99.2742(10)% 238U.[68]

Formation in nuclear reactors Edit

 
Table of nuclides: Buildup of actinides in a nuclear reactor, including radioative decay

The figure buildup of actinides is a table of nuclides with the number of neutrons on the horizontal axis (isotopes) and the number of protons on the vertical axis (elements). The red dot divides the nuclides in two groups, so the figure is more compact. Each nuclide is represented by a square with the mass number of the element and its half-life.[69] Naturally existing actinide isotopes (Th, U) are marked with a bold border, alpha emitters have a yellow colour, and beta emitters have a blue colour. Pink indicates electron capture (236Np), whereas white stands for a long-lasting metastable state (242Am).

The formation of actinide nuclides is primarily characterised by:[70]

  • Neutron capture reactions (n,γ), which are represented in the figure by a short right arrow.
  • The (n,2n) reactions and the less frequently occurring (γ,n) reactions are also taken into account, both of which are marked by a short left arrow.
  • Even more rarely and only triggered by fast neutrons, the (n,3n) reaction occurs, which is represented in the figure with one example, marked by a long left arrow.

In addition to these neutron- or gamma-induced nuclear reactions, the radioactive conversion of actinide nuclides also affects the nuclide inventory in a reactor. These decay types are marked in the figure by diagonal arrows. The beta-minus decay, marked with an arrow pointing up-left, plays a major role for the balance of the particle densities of the nuclides. Nuclides decaying by positron emission (beta-plus decay) or electron capture (ϵ) do not occur in a nuclear reactor except as products of knockout reactions; their decays are marked with arrows pointing down-right. Due to the long half-lives of the given nuclides, alpha decay plays almost no role in the formation and decay of the actinides in a power reactor, as the residence time of the nuclear fuel in the reactor core is rather short (a few years). Exceptions are the two relatively short-lived nuclides 242Cm (T1/2 = 163 d) and 236Pu (T1/2 = 2.9 y). Only for these two cases, the α decay is marked on the nuclide map by a long arrow pointing down-left. A few long-lived actinide isotopes, such as 244Pu and 250Cm, cannot be produced in reactors because neutron capture does not happen quickly enough to bypass the short-lived beta-decaying nuclides 243Pu and 249Cm; they can however be generated in nuclear explosions, which have much higher neutron fluxes.

Distribution in nature Edit

 
Unprocessed uranium ore

Thorium and uranium are the most abundant actinides in nature with the respective mass concentrations of 16 ppm and 4 ppm.[71] Uranium mostly occurs in the Earth's crust as a mixture of its oxides in the mineral uraninite, which is also called pitchblende because of its black color. There are several dozens of other uranium minerals such as carnotite (KUO2VO4·3H2O) and autunite (Ca(UO2)2(PO4)2·nH2O). The isotopic composition of natural uranium is 238U (relative abundance 99.2742%), 235U (0.7204%) and 234U (0.0054%); of these 238U has the largest half-life of 4.51×109 years.[72][73] The worldwide production of uranium in 2009 amounted to 50,572 tonnes, of which 27.3% was mined in Kazakhstan. Other important uranium mining countries are Canada (20.1%), Australia (15.7%), Namibia (9.1%), Russia (7.0%), and Niger (6.4%).[74]

Content of plutonium in uranium and thorium ores[75]
Ore Location Uranium
content, % 		Mass ratio
239Pu/ore 		Ratio
239Pu/U (×1012)
Uraninite Canada 13.5 9.1×10−12 7.1
Uraninite Congo 38 4.8×10−12 12
Uraninite Colorado, US 50 3.8×10−12 7.7
Monazite Brazil 0.24 2.1×10−14 8.3
Monazite North Carolina, US 1.64 5.9×10−14 3.6
Fergusonite - 0.25 <1×10−14 <4
Carnotite - 10 <4×10−14 <0.4

The most abundant thorium minerals are thorianite (ThO2), thorite (ThSiO4) and monazite, ((Th,Ca,Ce)PO4). Most thorium minerals contain uranium and vice versa; and they all have significant fraction of lanthanides. Rich deposits of thorium minerals are located in the United States (440,000 tonnes), Australia and India (~300,000 tonnes each) and Canada (~100,000 tonnes).[76]

The abundance of actinium in the Earth's crust is only about 5×10−15%.[61] Actinium is mostly present in uranium-containing, but also in other minerals, though in much smaller quantities. The content of actinium in most natural objects corresponds to the isotopic equilibrium of parent isotope 235U, and it is not affected by the weak Ac migration.[30] Protactinium is more abundant (10−12%) in the Earth's crust than actinium. It was discovered in the uranium ore in 1913 by Fajans and Göhring.[34] As actinium, the distribution of protactinium follows that of 235U.[61]

The half-life of the longest-lived isotope of neptunium, 237Np, is negligible compared to the age of the Earth. Thus neptunium is present in nature in negligible amounts produced as intermediate decay products of other isotopes.[38] Traces of plutonium in uranium minerals were first found in 1942, and the more systematic results on 239Pu are summarized in the table (no other plutonium isotopes could be detected in those samples). The upper limit of abundance of the longest-living isotope of plutonium, 244Pu, is 3×10−20%. Plutonium could not be detected in samples of lunar soil. Owing to its scarcity in nature, most plutonium is produced synthetically.[75]

Extraction Edit

 
Monazite: a major thorium mineral

Owing to the low abundance of actinides, their extraction is a complex, multistep process. Fluorides of actinides are usually used because they are insoluble in water and can be easily separated with redox reactions. Fluorides are reduced with calcium, magnesium or barium:[77]

 

Among the actinides, thorium and uranium are the easiest to isolate. Thorium is extracted mostly from monazite: thorium pyrophosphate (ThP2O7) is reacted with nitric acid, and the produced thorium nitrate treated with tributyl phosphate. Rare-earth impurities are separated by increasing the pH in sulfate solution.[77]

In another extraction method, monazite is decomposed with a 45% aqueous solution of sodium hydroxide at 140 °C. Mixed metal hydroxides are extracted first, filtered at 80 °C, washed with water and dissolved with concentrated hydrochloric acid. Next, the acidic solution is neutralized with hydroxides to pH = 5.8 that results in precipitation of thorium hydroxide (Th(OH)4) contaminated with ~3% of rare-earth hydroxides; the rest of rare-earth hydroxides remains in solution. Thorium hydroxide is dissolved in an inorganic acid and then purified from the rare earth elements. An efficient method is the dissolution of thorium hydroxide in nitric acid, because the resulting solution can be purified by extraction with organic solvents:[77]

 
Separation of uranium and plutonium from spent nuclear fuel using the PUREX process[78]
Th(OH)4 + 4 HNO3 → Th(NO3)4 + 4 H2O

Metallic thorium is separated from the anhydrous oxide, chloride or fluoride by reacting it with calcium in an inert atmosphere:[79]

ThO2 + 2 Ca → 2 CaO + Th

Sometimes thorium is extracted by electrolysis of a fluoride in a mixture of sodium and potassium chloride at 700–800 °C in a graphite crucible. Highly pure thorium can be extracted from its iodide with the crystal bar process.[80]

Uranium is extracted from its ores in various ways. In one method, the ore is burned and then reacted with nitric acid to convert uranium into a dissolved state. Treating the solution with a solution of tributyl phosphate (TBP) in kerosene transforms uranium into an organic form UO2(NO3)2(TBP)2. The insoluble impurities are filtered and the uranium is extracted by reaction with hydroxides as (NH4)2U2O7 or with hydrogen peroxide as UO4·2H2O.[77]

When the uranium ore is rich in such minerals as dolomite, magnesite, etc., those minerals consume much acid. In this case, the carbonate method is used for uranium extraction. Its main component is an aqueous solution of sodium carbonate, which converts uranium into a complex [UO2(CO3)3]4−, which is stable in aqueous solutions at low concentrations of hydroxide ions. The advantages of the sodium carbonate method are that the chemicals have low corrosivity (compared to nitrates) and that most non-uranium metals precipitate from the solution. The disadvantage is that tetravalent uranium compounds precipitate as well. Therefore, the uranium ore is treated with sodium carbonate at elevated temperature and under oxygen pressure:

2 UO2 + O2 + 6 CO2−
3 → 2 [UO2(CO3)3]4−

This equation suggests that the best solvent for the uranium carbonate processing is a mixture of carbonate with bicarbonate. At high pH, this results in precipitation of diuranate, which is treated with hydrogen in the presence of nickel yielding an insoluble uranium tetracarbonate.[77]

Another separation method uses polymeric resins as a polyelectrolyte. Ion exchange processes in the resins result in separation of uranium. Uranium from resins is washed with a solution of ammonium nitrate or nitric acid that yields uranyl nitrate, UO2(NO3)2·6H2O. When heated, it turns into UO3, which is converted to UO2 with hydrogen:

UO3 + H2 → UO2 + H2O

Reacting uranium dioxide with hydrofluoric acid changes it to uranium tetrafluoride, which yields uranium metal upon reaction with magnesium metal:[79]

4 HF + UO2 → UF4 + 2 H2O

To extract plutonium, neutron-irradiated uranium is dissolved in nitric acid, and a reducing agent (FeSO4, or H2O2) is added to the resulting solution. This addition changes the oxidation state of plutonium from +6 to +4, while uranium remains in the form of uranyl nitrate (UO2(NO3)2). The solution is treated with a reducing agent and neutralized with ammonium carbonate to pH = 8 that results in precipitation of Pu4+ compounds.[77]

In another method, Pu4+ and UO2+
2 are first extracted with tributyl phosphate, then reacted with hydrazine washing out the recovered plutonium.[77]

The major difficulty in separation of actinium is the similarity of its properties with those of lanthanum. Thus actinium is either synthesized in nuclear reactions from isotopes of radium or separated using ion-exchange procedures.[30]

Properties Edit

Actinides have similar properties to lanthanides. The 6d and 7s electronic shells are filled in actinium and thorium, and the 5f shell is being filled with further increase in atomic number; the 4f shell is filled in the lanthanides. The first experimental evidence for the filling of the 5f shell in actinides was obtained by McMillan and Abelson in 1940.[81] As in lanthanides (see lanthanide contraction), the ionic radius of actinides monotonically decreases with atomic number (see also Aufbau principle).[82]

Properties of actinides (the mass of the most long-lived isotope is in square brackets)[73][83]
Element Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
Core charge (Z) 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103
atomic mass [227] 232.0377(4) 231.03588(2) 238.02891(3) [237] [244] [243] [247] [247] [251] [252] [257] [258] [259] [266]
Number of natural isotopes[84] 3 7 3 8 3 4 0 0 0 0 0 0 0 0 0
Natural isotopes[84][85] 225, 227–228 227–232, 234 231, 233–234 233–240 237, 239–240 238–240, 244 — — — — — — — — —
Natural quantity isotopes — 230, 232 231 234, 235, 238 — — — — — — — — — — —
Longest-lived isotope 227 232 231 238 237 244 243 247 247 251 252 257 258 259 266
Half-life of the longest-lived isotope 21.8 years 14 billion years 32,500 years 4.47 billion years 2.14 million years 80.8 million years 7,370 years 15.6 million years 1,380 years 900 years 1.29 years 100.5 days 52 days 58 min 11 hours
Most common isotope 227 232 231 238 237 239 241 244 249 252 253 255 256 255 260
Half-life of the most common isotope 21.8 years 14 billion years 32,500 years 4.47 billion years 2.14 million years 24,100 years 433 years 18.1 years 320 days 2.64 years 20.47 days 20.07 hours 78 min 3.1 min 2.7 min
Electronic configuration in
the ground state (gas phase) 		6d17s2 6d27s2 5f26d17s2 5f36d17s2 5f46d17s2 5f67s2 5f77s2 5f76d17s2 5f97s2 5f107s2 5f117s2 5f127s2 5f137s2 5f147s2 5f147s27p1
Oxidation states 2, 3 2, 3, 4 2, 3, 4, 5 2, 3, 4, 5, 6 3, 4, 5, 6, 7 3, 4, 5, 6, 7 2, 3, 4, 5, 6, 7 2, 3, 4, 6 2, 3, 4 2, 3, 4 2, 3, 4 2, 3 2, 3 2, 3 3
Metallic radius (nm) 0.203 0.180 0.162 0.153 0.150 0.162 0.173 0.174 0.170 0.186 0.186 ? 0.198 ? 0.194 ? 0.197 ? 0.171
Ionic radius (nm):
An4+
An3+
—
0.126
0.114
—
0.104
0.118
0.103
0.118
0.101
0.116
0.100
0.115
0.099
0.114
0.099
0.112
0.097
0.110
0.096
0.109
0.085
0.098
0.084
0.091
0.084
0.090
0.084
0.095
0.083
0.088
Temperature (°C):
melting
boiling 		1050
3198		 1842
4788		 1568
? 4027		 1132.2
4131		 639
? 4174		 639.4
3228		 1176
? 2607		 1340
3110		 986
2627
900
? 1470		 860
? 996		 1530
—		 830
—		 830
—		 1630
—
Density, g/cm3 10.07 11.78 15.37 19.06 20.45 19.84 11.7 13.51 14.78 15.1 8.84 ? 9.7 ? 10.3 ? 9.9 ? 14.4
Standard electrode potential (V):
E° (An4+/An0)
E° (An3+/An0) 		—
−2.13
−1.83
—
−1.47
—
−1.38
−1.66
−1.30
−1.79
−1.25
−2.00
−0.90
−2.07
−0.75
−2.06
−0.55
−1.96
−0.59
−1.97
−0.36
−1.98
−0.29
−1.96
—
−1.74
—
−1.20
—
−2.10
Color:
[M(H2O)n]4+
[M(H2O)n]3+
—
Colorless
Colorless
Blue
Yellow
Dark blue
Green
Purple
Yellow-green
Purple
Brown
Violet
Red
Rose
Yellow
Colorless
Beige
Yellow-green
Green
Green
—
Pink
—
—
—
—
—
—
—
—
Approximate colors of actinide ions in aqueous solution
Colors for the actinides 100–103 are unknown as sufficient quantities have not yet been synthesized. The colour of CmO2+2 was likewise not recorded.

[86][87]

Actinide (Z) 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103
Oxidation state
+2 Fm2+ Md2+ No2+
+3 Ac3+ Th3+ Pa3+ U3+ Np3+ Pu3+ Am3+ Cm3+ Bk3+ Cf3+ Es3+ Fm3+ Md3+ No3+ Lr3+
+4 Th4+ Pa4+ U4+ Np4+ Pu4+ Am4+ Cm4+ Bk4+ Cf4+
+5 PaO+
2 		UO+
2 		NpO+
2 		PuO+
2 		AmO+
2
+6 UO2+
2 		NpO2+
2 		PuO2+
2 		AmO2+
2 		CmO2+
2
+7 NpO3+
2 		PuO3+
2 		AmO3−
5

Physical properties Edit

   
Major crystal structures of some actinides vs. temperature Metallic and ionic radii of actinides[83]
 
A pellet of 238PuO2 to be used in a radioisotope thermoelectric generator for either the Cassini or Galileo mission. The pellet produces 62 watts of heat and glows because of the heat generated by the radioactive decay (primarily α). Photo is taken after insulating the pellet under a graphite blanket for minutes and removing the blanket.
 
Californium

Actinides are typical metals. All of them are soft and have a silvery color (but tarnish in air),[88] relatively high density and plasticity. Some of them can be cut with a knife. Their electrical resistivity varies between 15 and 150 µΩ·cm.[83] The hardness of thorium is similar to that of soft steel, so heated pure thorium can be rolled in sheets and pulled into wire. Thorium is nearly half as dense as uranium and plutonium, but is harder than either of them. All actinides are radioactive, paramagnetic, and, with the exception of actinium, have several crystalline phases: plutonium has seven, and uranium, neptunium and californium three. The crystal structures of protactinium, uranium, neptunium and plutonium do not have clear analogs among the lanthanides and are more similar to those of the 3d-transition metals.[73]

All actinides are pyrophoric, especially when finely divided, that is, they spontaneously ignite upon reaction with air at room temperature.[88][89] The melting point of actinides does not have a clear dependence on the number of f-electrons. The unusually low melting point of neptunium and plutonium (~640 °C) is explained by hybridization of 5f and 6d orbitals and the formation of directional bonds in these metals.[73]

Chemical properties Edit

Like the lanthanides, all actinides are highly reactive with halogens and chalcogens; however, the actinides react more easily. Actinides, especially those with a small number of 5f-electrons, are prone to hybridization. This is explained by the similarity of the electron energies at the 5f, 7s and 6d shells. Most actinides exhibit a larger variety of valence states, and the most stable are +6 for uranium, +5 for protactinium and neptunium, +4 for thorium and plutonium and +3 for actinium and other actinides.[91]

Actinium is chemically similar to lanthanum, which is explained by their similar ionic radii and electronic structures. Like lanthanum, actinium almost always has an oxidation state of +3 in compounds, but it is less reactive and has more pronounced basic properties. Among other trivalent actinides Ac3+ is least acidic, i.e. has the weakest tendency to hydrolyze in aqueous solutions.[30][73]

Thorium is rather active chemically. Owing to lack of electrons on 6d and 5f orbitals, the tetravalent thorium compounds are colorless. At pH < 3, the solutions of thorium salts are dominated by the cations [Th(H2O)8]4+. The Th4+ ion is relatively large, and depending on the coordination number can have a radius between 0.95 and 1.14 Å. As a result, thorium salts have a weak tendency to hydrolyse. The distinctive ability of thorium salts is their high solubility both in water and polar organic solvents.[73]

Protactinium exhibits two valence states; the +5 is stable, and the +4 state easily oxidizes to protactinium(V). Thus tetravalent protactinium in solutions is obtained by the action of strong reducing agents in a hydrogen atmosphere. Tetravalent protactinium is chemically similar to uranium(IV) and thorium(IV). Fluorides, phosphates, hypophosphate, iodate and phenylarsonates of protactinium(IV) are insoluble in water and dilute acids. Protactinium forms soluble carbonates. The hydrolytic properties of pentavalent protactinium are close to those of tantalum(V) and niobium(V). The complex chemical behavior of protactinium is a consequence of the start of the filling of the 5f shell in this element.[61]

Uranium has a valence from 3 to 6, the last being most stable. In the hexavalent state, uranium is very similar to the group 6 elements. Many compounds of uranium(IV) and uranium(VI) are non-stoichiometric, i.e. have variable composition. For example, the actual chemical formula of uranium dioxide is UO2+x, where x varies between −0.4 and 0.32. Uranium(VI) compounds are weak oxidants. Most of them contain the linear "uranyl" group, UO2+
2. Between 4 and 6 ligands can be accommodated in an equatorial plane perpendicular to the uranyl group. The uranyl group acts as a hard acid and forms stronger complexes with oxygen-donor ligands than with nitrogen-donor ligands. NpO2+
2 and PuO2+
2 are also the common form of Np and Pu in the +6 oxidation state. Uranium(IV) compounds exhibit reducing properties, e.g., they are easily oxidized by atmospheric oxygen. Uranium(III) is a very strong reducing agent. Owing to the presence of d-shell, uranium (as well as many other actinides) forms organometallic compounds, such as UIII(C5H5)3 and UIV(C5H5)4.[73][92]

Neptunium has valence states from 3 to 7, which can be simultaneously observed in solutions. The most stable state in solution is +5, but the valence +4 is preferred in solid neptunium compounds. Neptunium metal is very reactive. Ions of neptunium are prone to hydrolysis and formation of coordination compounds.[38]

Plutonium also exhibits valence states between 3 and 7 inclusive, and thus is chemically similar to neptunium and uranium. It is highly reactive, and quickly forms an oxide film in air. Plutonium reacts with hydrogen even at temperatures as low as 25–50 °C; it also easily forms halides and intermetallic compounds. Hydrolysis reactions of plutonium ions of different oxidation states are quite diverse. Plutonium(V) can enter polymerization reactions.[93][94]

The largest chemical diversity among actinides is observed in americium, which can have valence between 2 and 6. Divalent americium is obtained only in dry compounds and non-aqueous solutions (acetonitrile). Oxidation states +3, +5 and +6 are typical for aqueous solutions, but also in the solid state. Tetravalent americium forms stable solid compounds (dioxide, fluoride and hydroxide) as well as complexes in aqueous solutions. It was reported that in alkaline solution americium can be oxidized to the heptavalent state, but these data proved erroneous. The most stable valence of americium is 3 in the aqueous solutions and 3 or 4 in solid compounds.[95]

Valence 3 is dominant in all subsequent elements up to lawrencium (with the exception of nobelium). Curium can be tetravalent in solids (fluoride, dioxide). Berkelium, along with a valence of +3, also shows the valence of +4, more stable than that of curium; the valence 4 is observed in solid fluoride and dioxide. The stability of Bk4+ in aqueous solution is close to that of Ce4+.[96] Only valence 3 was observed for californium, einsteinium and fermium. The divalent state is proven for mendelevium and nobelium, and in nobelium it is more stable than the trivalent state. Lawrencium shows valence 3 both in solutions and solids.[95]

The redox potential   increases from −0.32 V in uranium, through 0.34 V (Np) and 1.04 V (Pu) to 1.34 V in americium revealing the increasing reduction ability of the An4+ ion from americium to uranium. All actinides form AnH3 hydrides of black color with salt-like properties. Actinides also produce carbides with the general formula of AnC or AnC2 (U2C3 for uranium) as well as sulfides An2S3 and AnS2.[91]

  •  

    Uranyl nitrate (UO2(NO3)2)

  •  

    Aqueous solutions of uranium III, IV, V, VI salts

  •  

    Aqueous solutions of neptunium III, IV, V, VI, VII salts

  •  

    Aqueous solutions of plutonium III, IV, V, VI, VII salts

  •  

    Uranium tetrachloride

  •  

    Uranium hexafluoride

  •  

    U3O8 (yellowcake)

Compounds Edit

Oxides and hydroxides Edit

Dioxides of some actinides
Chemical formula ThO2 PaO2 UO2 NpO2 PuO2 AmO2 CmO2 BkO2 CfO2
CAS-number 1314-20-1 12036-03-2 1344-57-6 12035-79-9 12059-95-9 12005-67-3 12016-67-0 12010-84-3 12015-10-0
Molar mass 264.04 263.035 270.03 269.047 276.063 275.06 270–284** 279.069 283.078
Melting point[102] 3390 °C 2865 °C 2547 °C 2400 °C 2175 °C
Crystal structure  
An4+: __  /  O2−: __
Space group Fm3m
Coordination number An[8], O[4]
An – actinide
**Depending on the isotopes

Some actinides can exist in several oxide forms such as An2O3, AnO2, An2O5 and AnO3. For all actinides, oxides AnO3 are amphoteric and An2O3, AnO2 and An2O5 are basic, they easily react with water, forming bases:[91]

An2O3 + 3 H2O → 2 An(OH)3.

These bases are poorly soluble in water and by their activity are close to the hydroxides of rare-earth metals.[91] Np(OH)3 has not yet been synthesized, Pu(OH)3 has a blue color while Am(OH)3 is pink and curium hydroxide Cm(OH)3 is colorless.[103] Bk(OH)3 and Cf(OH)3 are also known, as are tetravalent hydroxides for Np, Pu and Am and pentavalent for Np and Am.[103]

The strongest base is of actinium. All compounds of actinium are colorless, except for black actinium sulfide (Ac2S3).[91] Dioxides of tetravalent actinides crystallize in the cubic system, same as in calcium fluoride.

Thorium reacting with oxygen exclusively forms the dioxide:

 

Thorium dioxide is a refractory material with the highest melting point among any known oxide (3390 °C).[101] Adding 0.8–1% ThO2 to tungsten stabilizes its structure, so the doped filaments have better mechanical stability to vibrations. To dissolve ThO2 in acids, it is heated to 500–600 °C; heating above 600 °C produces a very resistant to acids and other reagents form of ThO2. Small addition of fluoride ions catalyses dissolution of thorium dioxide in acids.

Two protactinium oxides have been obtained: PaO2 (black) and Pa2O5 (white); the former is isomorphic with ThO2 and the latter is easier to obtain. Both oxides are basic, and Pa(OH)5 is a weak, poorly soluble base.[91]

Decomposition of certain salts of uranium, for example UO2(NO3)·6H2O in air at 400 °C, yields orange or yellow UO3.[101] This oxide is amphoteric and forms several hydroxides, the most stable being uranyl hydroxide UO2(OH)2. Reaction of uranium(VI) oxide with hydrogen results in uranium dioxide, which is similar in its properties with ThO2. This oxide is also basic and corresponds to the uranium hydroxide (U(OH)4).[91]

Plutonium, neptunium and americium form two basic oxides: An2O3 and AnO2. Neptunium trioxide is unstable; thus, only Np3O8 could be obtained so far. However, the oxides of plutonium and neptunium with the chemical formula AnO2 and An2O3 are well characterized.[91]

Salts Edit

Trichlorides of some actinides[104]
Chemical formula AcCl3 UCl3 NpCl3 PuCl3 AmCl3 CmCl3 BkCl3 CfCl3
CAS-number 22986-54-5 10025-93-1 20737-06-8 13569-62-5 13464-46-5 13537-20-7 13536-46-4 13536-90-8
Molar mass 333.386 344.387 343.406 350.32 349.42 344–358** 353.428 357.438
Melting point 837 °C 800 °C 767 °C 715 °C 695 °C 603 °C 545 °C
Boiling point 1657 °C 1767 °C 850 °C
Crystal structure  
An3+: __  /  Cl−: __
Space group P63/m
Coordination number An*[9], Cl [3]
Lattice constants a = 762 pm
c = 455 pm		 a = 745.2 pm
c = 432.8 pm		 a = 739.4 pm
c = 424.3 pm		 a = 738.2 pm
c = 421.4 pm		 a = 726 pm
c = 414 pm		 a = 738.2 pm
c = 412.7 pm		 a = 738 pm
c = 409 pm
*An – actinide
**Depending on the isotopes
 
Einsteinium triiodide glowing in the dark

Actinides easily react with halogens forming salts with the formulas MX3 and MX4 (X = halogen). So the first berkelium compound, BkCl3, was synthesized in 1962 with an amount of 3 nanograms. Like the halogens of rare earth elements, actinide chlorides, bromides, and iodides are water-soluble, and fluorides are insoluble. Uranium easily yields a colorless hexafluoride, which sublimates at a temperature of 56.5 °C; because of its volatility, it is used in the separation of uranium isotopes with gas centrifuge or gaseous diffusion. Actinide hexafluorides have properties close to anhydrides. They are very sensitive to moisture and hydrolyze forming AnO2F2.[107] The pentachloride and black hexachloride of uranium were synthesized, but they are both unstable.[91]

Action of acids on actinides yields salts, and if the acids are non-oxidizing then the actinide in the salt is in low-valence state:

U + 2 H2SO4 → U(SO4)2 + 2 H2
2 Pu + 6 HCl → 2 PuCl3 + 3 H2

However, in these reactions the regenerating hydrogen can react with the metal, forming the corresponding hydride. Uranium reacts with acids and water much more easily than thorium.[91]

Actinide salts can also be obtained by dissolving the corresponding hydroxides in acids. Nitrates, chlorides, sulfates and perchlorates of actinides are water-soluble. When crystallizing from aqueous solutions, these salts forming a hydrates, such as Th(NO3)4·6H2O, Th(SO4)2·9H2O and Pu2(SO4)3·7H2O. Salts of high-valence actinides easily hydrolyze. So, colorless sulfate, chloride, perchlorate and nitrate of thorium transform into basic salts with formulas Th(OH)2SO4 and Th(OH)3NO3. The solubility and insolubility of trivalent and tetravalent actinides is like that of lanthanide salts. So phosphates, fluorides, oxalates, iodates and carbonates of actinides are weakly soluble in water; they precipitate as hydrates, such as ThF4·3H2O and Th(CrO4)2·3H2O.[91]

Actinides with oxidation state +6, except for the AnO22+-type cations, form [AnO4]2−, [An2O7]2− and other complex anions. For example, uranium, neptunium and plutonium form salts of the Na2UO4 (uranate) and (NH4)2U2O7 (diuranate) types. In comparison with lanthanides, actinides more easily form coordination compounds, and this ability increases with the actinide valence. Trivalent actinides do not form fluoride coordination compounds, whereas tetravalent thorium forms K2ThF6, KThF5, and even K5ThF9 complexes. Thorium also forms the corresponding sulfates (for example Na2SO4·Th(SO4)2·5H2O), nitrates and thiocyanates. Salts with the general formula An2Th(NO3)6·nH2O are of coordination nature, with the coordination number of thorium equal to 12. Even easier is to produce complex salts of pentavalent and hexavalent actinides. The most stable coordination compounds of actinides – tetravalent thorium and uranium – are obtained in reactions with diketones, e.g. acetylacetone.[91]

Applications Edit

 
Interior of a smoke detector containing americium-241.

While actinides have some established daily-life applications, such as in smoke detectors (americium)[108][109] and gas mantles (thorium),[79] they are mostly used in nuclear weapons and as fuel in nuclear reactors.[79] The last two areas exploit the property of actinides to release enormous energy in nuclear reactions, which under certain conditions may become self-sustaining chain reactions.

 
Self-illumination of a nuclear reactor by Cherenkov radiation.

The most important isotope for nuclear power applications is uranium-235. It is used in the thermal reactor, and its concentration in natural uranium does not exceed 0.72%. This isotope strongly absorbs thermal neutrons releasing much energy. One fission act of 1 gram of 235U converts into about 1 MW·day. Of importance, is that 235
92U
 emits more neutrons than it absorbs;[110] upon reaching the critical mass, 235
92U
 enters into a self-sustaining chain reaction.[73] Typically, uranium nucleus is divided into two fragments with the release of 2–3 neutrons, for example:

235
92U
 + 1
0n
 ⟶ 115
45Rh
 + 118
47Ag
 + 31
0n

Other promising actinide isotopes for nuclear power are thorium-232 and its product from the thorium fuel cycle, uranium-233.

Nuclear reactor[73][111][112]
The core of most Generation II nuclear reactors contains a set of hollow metal rods, usually made of zirconium alloys, filled with solid nuclear fuel pellets – mostly oxide, carbide, nitride or monosulfide of uranium, plutonium or thorium, or their mixture (the so-called MOX fuel). The most common fuel is oxide of uranium-235.
 
Nuclear reactor scheme

Fast neutrons are slowed by moderators, which contain water, carbon, deuterium, or beryllium, as thermal neutrons to increase the efficiency of their interaction with uranium-235. The rate of nuclear reaction is controlled by introducing additional rods made of boron or cadmium or a liquid absorbent, usually boric acid. Reactors for plutonium production are called breeder reactor or breeders; they have a different design and use fast neutrons.

Emission of neutrons during the fission of uranium is important not only for maintaining the nuclear chain reaction, but also for the synthesis of the heavier actinides. Uranium-239 converts via β-decay into plutonium-239, which, like uranium-235, is capable of spontaneous fission. The world's first nuclear reactors were built not for energy, but for producing plutonium-239 for nuclear weapons.

About half of the produced thorium is used as the light-emitting material of gas mantles.[79] Thorium is also added into multicomponent alloys of magnesium and zinc. So the Mg-Th alloys are light and strong, but also have high melting point and ductility and thus are widely used in the aviation industry and in the production of missiles. Thorium also has good electron emission properties, with long lifetime and low potential barrier for the emission.[110] The relative content of thorium and uranium isotopes is widely used to estimate the age of various objects, including stars (see radiometric dating).[113]

The major application of plutonium has been in nuclear weapons, where the isotope plutonium-239 was a key component due to its ease of fission and availability. Plutonium-based designs allow reducing the critical mass to about a third of that for uranium-235.[114] The "Fat Man"-type plutonium bombs produced during the Manhattan Project used explosive compression of plutonium to obtain significantly higher densities than normal, combined with a central neutron source to begin the reaction and increase efficiency. Thus only 6.2 kg of plutonium was needed for an explosive yield equivalent to 20 kilotons of TNT.[115] (See also Nuclear weapon design.) Hypothetically, as little as 4 kg of plutonium—and maybe even less—could be used to make a single atomic bomb using very sophisticated assembly designs.[116]

Plutonium-238 is potentially more efficient isotope for nuclear reactors, since it has smaller critical mass than uranium-235, but it continues to release much thermal energy (0.56 W/g)[109][117] by decay even when the fission chain reaction is stopped by control rods. Its application is limited by its high price (about US$1000/g). This isotope has been used in thermopiles and water distillation systems of some space satellites and stations. So Galileo and Apollo spacecraft (e.g. Apollo 14[118]) had heaters powered by kilogram quantities of plutonium-238 oxide; this heat is also transformed into electricity with thermopiles. The decay of plutonium-238 produces relatively harmless alpha particles and is not accompanied by gamma-irradiation. Therefore, this isotope (~160 mg) is used as the energy source in heart pacemakers where it lasts about 5 times longer than conventional batteries.[109]

Actinium-227 is used as a neutron source. Its high specific energy (14.5 W/g) and the possibility of obtaining significant quantities of thermally stable compounds are attractive for use in long-lasting thermoelectric generators for remote use. 228Ac is used as an indicator of radioactivity in chemical research, as it emits high-energy electrons (2.18 MeV) that can be easily detected. 228Ac-228Ra mixtures are widely used as an intense gamma-source in industry and medicine.[30]

Development of self-glowing actinide-doped materials with durable crystalline matrices is a new area of actinide utilization as the addition of alpha-emitting radionuclides to some glasses and crystals may confer luminescence.[119]

Toxicity Edit

 
Schematic illustration of penetration of radiation through sheets of paper, aluminium and lead brick
 
Periodic table with elements colored according to the half-life of their most stable isotope.
  Elements which contain at least one stable isotope.
  Slightly radioactive elements: the most stable isotope is very long-lived, with a half-life of over two million years.
  Significantly radioactive elements: the most stable isotope has half-life between 800 and 34,000 years.
  Radioactive elements: the most stable isotope has half-life between one day and 130 years.
  Highly radioactive elements: the most stable isotope has half-life between several minutes and one day.
  Extremely radioactive elements: the most stable known isotope has half-life less than several minutes.

Radioactive substances can harm human health via (i) local skin contamination, (ii) internal exposure due to ingestion of radioactive isotopes, and (iii) external overexposure by β-activity and γ-radiation. Together with radium and transuranium elements, actinium is one of the most dangerous radioactive poisons with high specific α-activity. The most important feature of actinium is its ability to accumulate and remain in the surface layer of skeletons. At the initial stage of poisoning, actinium accumulates in the liver. Another danger of actinium is that it undergoes radioactive decay faster than being excreted. Adsorption from the digestive tract is much smaller (~0.05%) for actinium than radium.[30]

Protactinium in the body tends to accumulate in the kidneys and bones. The maximum safe dose of protactinium in the human body is 0.03 µCi that corresponds to 0.5 micrograms of 231Pa. This isotope, which might be present in the air as aerosol, is 2.5×108 times more toxic than hydrocyanic acid.[61][contradictory]

Plutonium, when entering the body through air, food or blood (e.g. a wound), mostly settles in the lungs, liver and bones with only about 10% going to other organs, and remains there for decades. The long residence time of plutonium in the body is partly explained by its poor solubility in water. Some isotopes of plutonium emit ionizing α-radiation, which damages the surrounding cells. The median lethal dose (LD50) for 30 days in dogs after intravenous injection of plutonium is 0.32 milligram per kg of body mass, and thus the lethal dose for humans is approximately 22 mg for a person weighing 70 kg; the amount for respiratory exposure should be approximately four times greater. Another estimate assumes that plutonium is 50 times less toxic than radium, and thus permissible content of plutonium in the body should be 5 µg or 0.3 µCi. Such amount is nearly invisible under microscope. After trials on animals, this maximum permissible dose was reduced to 0.65 µg or 0.04 µCi. Studies on animals also revealed that the most dangerous plutonium exposure route is through inhalation, after which 5–25% of inhaled substances is retained in the body. Depending on the particle size and solubility of the plutonium compounds, plutonium is localized either in the lungs or in the lymphatic system, or is absorbed in the blood and then transported to the liver and bones. Contamination via food is the least likely way. In this case, only about 0.05% of soluble 0.01% insoluble compounds of plutonium absorbs into blood, and the rest is excreted. Exposure of damaged skin to plutonium would retain nearly 100% of it.[93]

Using actinides in nuclear fuel, sealed radioactive sources or advanced materials such as self-glowing crystals has many potential benefits. However, a serious concern is the extremely high radiotoxicity of actinides and their migration in the environment.[120] Use of chemically unstable forms of actinides in MOX and sealed radioactive sources is not appropriate by modern safety standards. There is a challenge to develop stable and durable actinide-bearing materials, which provide safe storage, use and final disposal. A key need is application of actinide solid solutions in durable crystalline host phases.[119]

Nuclear properties Edit

Half-lives and branching fractions for actinides and natural decay products[121]
Nuclide Half-life Decay mode Branching fraction Source
206
81Tl
 4.202 ± 0.011 m β− 1.0 LNHB
208
81Tl
 3.060 ± 0.008 m β− 1.0 BIPM-5
210
82Pb
 22.20 ± 0.22 y β− 1.0 ENSDF
α ( 1.9 ± 0.4 ) x 10−8
211
82Pb
 36.1 ± 0.2 m β− 1.0 ENSDF
212
82Pb
 10.64 ± 0.01 h β− 1.0 BIPM-5
214
82Pb
 26.8 ± 0.9 m β− 1.0 ENSDF
211
83Bi
 2.14 ± 0.02 m β− 0.00276 ± 0.00004 ENSDF
α 0.99724 ± 0.00004
212
83Bi
 60.54 ± 0.06 m α 0.3593 ± 0.0007 BIPM-5
β− 0.6407 ± 0.0007
214
83Bi
 19.9 ± 0.4 m α 0.00021 ± 0.00001 ENSDF
β− 0.99979 ± 0.00001
210
84Po
 138.376 ± 0.002 d α 1.0 ENSDF
219
86Rn
 3.96 ± 0.01 s α 1.0 ENSDF
220
86Rn
 55.8 ± 0.3 s α 1.0 BIPM-5
221
87Fr
 4.9 ± 0.2 m β− 0.00005 ± 0.00003 ENSDF
α 0.99995 ± 0.00003
223
88Ra
 11.43 ± 0.05 d α 1.0 ENSDF
14C ( 8.9 ± 0.4 ) x 10−10
224
88Ra
 3.627 ± 0.007 d α 1.0 BIPM-5
225
88Ra
 14.9 ± 0.2 d β− 1.0 ENSDF
226
88Ra
 ( 1.600 ± 0.007 ) x 103 y α 1.0 BIPM-5
228
88Ra
 5.75 ± 0.03 y β− 1.0 ENSDF
224
89Ac
 2.78 ± 0.17 h α 0.091 +0.020 -0.014 ENSDF
EC 0.909 +0.014 -0.020
225
89Ac
 10.0 ± 0.1 d α 1.0 ENSDF
227
89Ac
 21.772 ± 0.003 y α 0.01380 ± 0.00004 ENSDF
β− 0.98620 ± 0.00004
228
89Ac
 6.15 ± 0.02 h β− 1.0 ENSDF
227
90Th
 18.718 ± 0.005 d α 1.0 BIPM-5
228
90Th
 698.60 ± 0.23 d α 1.0 BIPM-5
229
90Th
 ( 7.34 ± 0.16 ) x 103 y α 1.0 ENSDF
230
90Th
 ( 7.538 ± 0.030 ) x 104 y α 1.0 ENSDF
SF ≤ 4 x 10−13
231
90Th
 25.52 ± 0.01 h β− 1.0 ENSDF
α ~ 4 x 10−13
232
90Th
 ( 1.405 ± 0.006 ) x 1010 y α 1.0 ENSDF
SF ( 1.1 ± 0.4 ) x 10−11
233
90Th
 22.15 ± 0.15 m β− 1.0 LNHB
234
90Th
 24.10 ± 0.03 d β− 1.0 ENSDF
231
91Pa
 ( 3.276 ± 0.011 ) x 104 y α 1.0 ENSDF
SF ≤ 3 x 10−12
232
91Pa
 1.32 ± 0.02 d EC 0.00003 ± 0.00001 ENSDF
β− 0.99997 ± 0.00001
233
91Pa
 26.98 ± 0.02 d β− 1.0 LNHB
234
91Pa
 6.70 ± 0.05 h β− 1.0 ENSDF
234m
91Pa
 1.159 ± 0.016 m IT 0.0016 ± 0.0002 IAEA-CRP-XG
β− 0.9984 ± 0.0002
232
92U
 68.9 ± 0.4 y α 1.0 ENSDF
SF
233
92U
 ( 1.592 ± 0.002 ) x 105 y α 1.0 ENSDF
SF
234
92U
 ( 2.455 ± 0.006 ) x 105 y α 1.0 LNHB
SF ( 1.6 ± 0.2 ) x 10−11
235m
92U
 26 ± 1 m IT 1.0 ENSDF
235
92U
 ( 7.038 ± 0.005 ) x 108 y α 1.0 ENSDF
SF ( 7 ± 2 ) x 10−11
236
92U
 ( 2.342 ± 0.004 ) x 107 y α 1.0 ENSDF
SF ( 9.4 ± 0.4 ) x 10−10
237
92U
 6.749 ± 0.016 d β− 1.0 LNHB
238
92U
 ( 4.468 ± 0.005 ) x 109 y α 1.0 LNHB
SF ( 5.45 ± 0.04 ) x 10−7
239
92U
 23.45 ± 0.02 m β− 1.0 ENSDF
236
93Np
 ( 1.55 ± 0.08 ) x 105 y α 0.0016 ± 0.0006 LNHB
β− 0.120 ± 0.006
EC 0.878 ± 0.006
236m
93Np
 22.5 ± 0.4 h β− 0.47 ± 0.01 LNHB
EC 0.53 ± 0.01
237
93Np
 ( 2.144 ± 0.007 ) x 106 y α 1.0 ENSDF
SF
238
93Np
 2.117 ± 0.002 d β− 1.0 ENSDF
239
93Np
 2.356 ± 0.003 d β− 1.0 ENSDF
236
94Pu
 2.858 ± 0.008 y α 1.0 ENSDF
References
LNHB Laboratoire National Henri Becquerel, Recommended Data,

http://www.nucleide.org/DDEP_WG/DDEPdata.htm 13 February 2021 at the Wayback Machine, 3 October 2006.

BIPM-5 M.-M. Bé, V. Chisté, C. Dulieu, E. Browne, V. Chechev, N. Kuzmenko, R. Helmer,

A. Nichols, E. Schönfeld, R. Dersch, Monographie BIPM-5, Table of Radionuclides, Vol. 2 – A = 151 to 242, 2004.

ENSDF "Evaluated Nuclear Structure Data File". Brookhaven National Laboratory. Retrieved 15 November 2006.
IAEA-CRP-XG M.-M. Bé, V. P. Chechev, R. Dersch, O. A. M. Helene, R. G. Helmer, M. Herman,

S. Hlavác, A. Marcinkowski, G. L. Molnár, A. L. Nichols, E. Schönfeld, V. R. Vanin, M. J. Woods, IAEA CRP "Update of X Ray and Gamma Ray Decay Data Standards for Detector Calibration and Other Applications", IAEA Scientific and Technical Information report STI/PUB/1287, May 2007, International Atomic Energy Agency, Vienna, Austria, ISBN 92-0-113606-4.

See also Edit

Notes Edit

  1. ^ Nobelium and lawrencium were almost simultaneously discovered by Soviet and American scientists
  2. ^ Specific activity is calculated by given in the table half-lives and the probability of spontaneous fission

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  • Los Alamos National Laboratory, Actinide Research Quarterly

October 15, 2023
actinide, periodic, table, hydrogen, heliumlithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, neonsodium, magnesium, aluminium, silicon, phosphorus, sulfur, chlorine, argonpotassium, calcium, scandium, titanium, vanadium, chromium, manganese, iron,. Actinides in the periodic table Hydrogen HeliumLithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine NeonSodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine ArgonPotassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine KryptonRubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine XenonCaesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury element Thallium Lead Bismuth Polonium Astatine RadonFrancium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson The actinide ˈ ae k t ɪ n aɪ d or actinoid ˈ ae k t ɪ n ɔɪ d series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103 actinium through lawrencium The actinide series derives its name from the first element in the series actinium The informal chemical symbol An is used in general discussions of actinide chemistry to refer to any actinide 1 2 3 The 1985 IUPAC Red Book recommends that actinoid be used rather than actinide since the suffix ide normally indicates a negative ion However owing to widespread current use actinide is still allowed Since actinoid literally means actinium like cf humanoid or android it has been argued for semantic reasons that actinium cannot logically be an actinoid but IUPAC acknowledges its inclusion based on common usage 4 All the actinides are f block elements except the final one lawrencium which is a d block element 5 6 on this basis the inclusion of lawrencium among the actinides has sometimes been questioned 7 as it is also a transition metal The series mostly corresponds to the filling of the 5f electron shell although in the ground state many have anomalous configurations involving the filling of the 6d shell due to interelectronic repulsion In comparison with the lanthanides also mostly f block elements the actinides show much more variable valence They all have very large atomic and ionic radii and exhibit an unusually large range of physical properties While actinium and the late actinides from americium onwards behave similarly to the lanthanides the elements thorium protactinium and uranium are much more similar to transition metals in their chemistry with neptunium and plutonium occupying an intermediate position All actinides are radioactive and release energy upon radioactive decay naturally occurring uranium and thorium and synthetically produced plutonium are the most abundant actinides on Earth These are used in nuclear reactors and nuclear weapons Uranium and thorium also have diverse current or historical uses and americium is used in the ionization chambers of most modern smoke detectors Of the actinides primordial thorium and uranium occur naturally in substantial quantities The radioactive decay of uranium produces transient amounts of actinium and protactinium and atoms of neptunium and plutonium are occasionally produced from transmutation reactions in uranium ores The other actinides are purely synthetic elements 1 8 Nuclear weapons tests have released at least six actinides heavier than plutonium into the environment analysis of debris from a 1952 hydrogen bomb explosion showed the presence of americium curium berkelium californium einsteinium and fermium 9 In presentations of the periodic table the f block elements are customarily shown as two additional rows below the main body of the table 1 This convention is entirely a matter of aesthetics and formatting practicality a rarely used wide formatted periodic table inserts the 4f and 5f series in their proper places as parts of the table s sixth and seventh rows periods vteActinides Actin ium 89 Ac 227 Thor ium 90 Th 232 04 Protac tinium 91 Pa 231 04 Ura nium 92 U 238 03 Neptu nium 93 Np 237 Pluto nium 94 Pu 244 Ameri cium 95 Am 243 Curium 96 Cm 247 Berkel ium 97 Bk 247 Califor nium 98 Cf 251 Einstei nium 99 Es 252 Fer mium 100 Fm 257 Mende levium 101 Md 258 Nobel ium 102 No 259 Lawren cium 103 Lr 266 Primordial From decay Synthetic Border shows natural occurrence of the element Contents 1 Discovery isolation and synthesis 1 1 From actinium to uranium 1 2 Neptunium and above 2 Isotopes 3 Formation in nuclear reactors 4 Distribution in nature 5 Extraction 6 Properties 6 1 Physical properties 6 2 Chemical properties 7 Compounds 7 1 Oxides and hydroxides 7 2 Salts 8 Applications 9 Toxicity 10 Nuclear properties 11 See also 12 Notes 13 References 14 Bibliography 15 External linksDiscovery isolation and synthesis EditSynthesis of transuranium elements 10 notes 1 Element Year MethodNeptunium 1940 Bombarding 238U by neutronsPlutonium 1941 Bombarding 238U by deuteronsAmericium 1944 Bombarding 239Pu by neutronsCurium 1944 Bombarding 239Pu by a particlesBerkelium 1949 Bombarding 241Am by a particlesCalifornium 1950 Bombarding 242Cm by a particlesEinsteinium 1952 As a product of nuclear explosionFermium 1952 As a product of nuclear explosionMendelevium 1955 Bombarding 253Es by a particlesNobelium 1965 Bombarding 243Am by 15N or 238U with 22NeLawrencium 1961 1971 Bombarding 252Cf by 10B or 11Band of 243Am with 18OLike the lanthanides the actinides form a family of elements with similar properties Within the actinides there are two overlapping groups transuranium elements which follow uranium in the periodic table and transplutonium elements which follow plutonium Compared to the lanthanides which except for promethium are found in nature in appreciable quantities most actinides are rare Most do not occur in nature and of those that do only thorium and uranium do so in more than trace quantities The most abundant or easily synthesized actinides are uranium and thorium followed by plutonium americium actinium protactinium neptunium and curium 11 The existence of transuranium elements was suggested in 1934 by Enrico Fermi based on his experiments 12 13 However even though four actinides were known by that time it was not yet understood that they formed a family similar to lanthanides The prevailing view that dominated early research into transuranics was that they were regular elements in the 7th period with thorium protactinium and uranium corresponding to 6th period hafnium tantalum and tungsten respectively Synthesis of transuranics gradually undermined this point of view By 1944 an observation that curium failed to exhibit oxidation states above 4 whereas its supposed 6th period homolog platinum can reach oxidation state of 6 prompted Glenn Seaborg to formulate an actinide hypothesis Studies of known actinides and discoveries of further transuranic elements provided more data in support of this position but the phrase actinide hypothesis the implication being that a hypothesis is something that has not been decisively proven remained in active use by scientists through the late 1950s 14 15 At present there are two major methods of producing isotopes of transplutonium elements 1 irradiation of the lighter elements with neutrons 2 irradiation with accelerated charged particles The first method is more important for applications as only neutron irradiation using nuclear reactors allows the production of sizeable amounts of synthetic actinides however it is limited to relatively light elements The advantage of the second method is that elements heavier than plutonium as well as neutron deficient isotopes can be obtained which are not formed during neutron irradiation 16 In 1962 1966 there were attempts in the United States to produce transplutonium isotopes using a series of six underground nuclear explosions Small samples of rock were extracted from the blast area immediately after the test to study the explosion products but no isotopes with mass number greater than 257 could be detected despite predictions that such isotopes would have relatively long half lives of a decay This non observation was attributed to spontaneous fission owing to the large speed of the products and to other decay channels such as neutron emission and nuclear fission 17 From actinium to uranium Edit nbsp Enrico Fermi suggested the existence of transuranium elements in 1934 Uranium and thorium were the first actinides discovered Uranium was identified in 1789 by the German chemist Martin Heinrich Klaproth in pitchblende ore He named it after the planet Uranus 8 which had been discovered eight years earlier Klaproth was able to precipitate a yellow compound likely sodium diuranate by dissolving pitchblende in nitric acid and neutralizing the solution with sodium hydroxide He then reduced the obtained yellow powder with charcoal and extracted a black substance that he mistook for metal 18 Sixty years later the French scientist Eugene Melchior Peligot identified it as uranium oxide He also isolated the first sample of uranium metal by heating uranium tetrachloride with metallic potassium 19 The atomic mass of uranium was then calculated as 120 but Dmitri Mendeleev in 1872 corrected it to 240 using his periodicity laws This value was confirmed experimentally in 1882 by K Zimmerman 20 21 Thorium oxide was discovered by Friedrich Wohler in the mineral thorianite which was found in Norway 1827 22 Jons Jacob Berzelius characterized this material in more detail in 1828 By reduction of thorium tetrachloride with potassium he isolated the metal and named it thorium after the Norse god of thunder and lightning Thor 23 24 The same isolation method was later used by Peligot for uranium 8 Actinium was discovered in 1899 by Andre Louis Debierne an assistant of Marie Curie in the pitchblende waste left after removal of radium and polonium He described the substance in 1899 as similar to titanium 25 and in 1900 as similar to thorium 26 The discovery of actinium by Debierne was however questioned in 1971 27 and 2000 28 arguing that Debierne s publications in 1904 contradicted his earlier work of 1899 1900 This view instead credits the 1902 work of Friedrich Oskar Giesel who discovered a radioactive element named emanium that behaved similarly to lanthanum The name actinium comes from the Ancient Greek aktis aktinos aktis aktinos meaning beam or ray This metal was discovered not by its own radiation but by the radiation of the daughter products 29 30 Owing to the close similarity of actinium and lanthanum and low abundance pure actinium could only be produced in 1950 The term actinide was probably introduced by Victor Goldschmidt in 1937 31 32 Protactinium was possibly isolated in 1900 by William Crookes 33 It was first identified in 1913 when Kasimir Fajans and Oswald Helmuth Gohring encountered the short lived isotope 234mPa half life 1 17 minutes during their studies of the 238U decay They named the new element brevium from Latin brevis meaning brief 34 35 the name was changed to protoactinium from Greek prῶtos ἀktis meaning first beam element in 1918 when two groups of scientists led by the Austrian Lise Meitner and Otto Hahn of Germany and Frederick Soddy and John Cranston of Great Britain independently discovered the much longer lived 231Pa The name was shortened to protactinium in 1949 This element was little characterized until 1960 when A G Maddock and his co workers in the U K isolated 130 grams of protactinium from 60 tonnes of waste left after extraction of uranium from its ore 36 Neptunium and above Edit Neptunium named for the planet Neptune the next planet out from Uranus after which uranium was named was discovered by Edwin McMillan and Philip H Abelson in 1940 in Berkeley California 37 They produced the 239Np isotope half life 2 4 days by bombarding uranium with slow neutrons 36 It was the first transuranium element produced synthetically 38 nbsp Glenn T Seaborg and his group at the University of California at Berkeley synthesized Pu Am Cm Bk Cf Es Fm Md No and element 106 which was later named seaborgium in his honor while he was still living They also synthesized more than a hundred actinide isotopes Transuranium elements do not occur in sizeable quantities in nature and are commonly synthesized via nuclear reactions conducted with nuclear reactors For example under irradiation with reactor neutrons uranium 238 partially converts to plutonium 239 U 92 238 n 0 1 U 92 239 23 5 min b Np 93 239 2 3 days b Pu 94 239 2 4 10 4 years a U 92 235 displaystyle ce 238 92 U 0 1 n gt 92 239 U gt beta 23 5 ce min 93 239 Np gt beta 2 3 ce days 94 239 Pu left ce gt alpha 2 4 cdot 10 4 ce years right ce 235 92 U nbsp This synthesis reaction was used by Fermi and his collaborators in their design of the reactors located at the Hanford Site which produced significant amounts of plutonium 239 for the nuclear weapons of the Manhattan Project and the United States post war nuclear arsenal 39 Actinides with the highest mass numbers are synthesized by bombarding uranium plutonium curium and californium with ions of nitrogen oxygen carbon neon or boron in a particle accelerator Thus nobelium was produced by bombarding uranium 238 with neon 22 as U 92 238 Ne 10 22 No 102 256 4 0 1 n displaystyle ce 92 238 U 10 22 Ne gt 102 256 No 4 0 1n nbsp The first isotopes of transplutonium elements americium 241 and curium 242 were synthesized in 1944 by Glenn T Seaborg Ralph A James and Albert Ghiorso 40 Curium 242 was obtained by bombarding plutonium 239 with 32 MeV a particles Pu 94 239 He 2 4 Cm 96 242 n 0 1 displaystyle ce 94 239 Pu 2 4He gt 96 242 Cm 0 1n nbsp The americium 241 and curium 242 isotopes also were produced by irradiating plutonium in a nuclear reactor The latter element was named after Marie Curie and her husband Pierre who are noted for discovering radium and for their work in radioactivity 41 Bombarding curium 242 with a particles resulted in an isotope of californium 245Cf 1950 and a similar procedure yielded in 1949 berkelium 243 from americium 241 42 The new elements were named after Berkeley California by analogy with its lanthanide homologue terbium which was named after the village of Ytterby in Sweden 43 In 1945 B B Cunningham obtained the first bulk chemical compound of a transplutonium element namely americium hydroxide 44 Over the few years milligram quantities of americium and microgram amounts of curium were accumulated that allowed production of isotopes of berkelium Thomson 1949 45 46 and californium Thomson 1950 47 48 49 Sizeable amounts of these elements were produced in 1958 Burris B Cunningham and Stanley G Thomson 50 and the first californium compound 0 3 µg of CfOCl was obtained in 1960 by B B Cunningham and J C Wallmann 51 Einsteinium and fermium were identified in 1952 1953 in the fallout from the Ivy Mike nuclear test 1 November 1952 the first successful test of a hydrogen bomb Instantaneous exposure of uranium 238 to a large neutron flux resulting from the explosion produced heavy isotopes of uranium including uranium 253 and uranium 255 and their b decay yielded einsteinium 253 and fermium 255 The discovery of the new elements and the new data on neutron capture were initially kept secret on the orders of the US military until 1955 due to Cold War tensions 9 52 Nevertheless the Berkeley team were able to prepare einsteinium and fermium by civilian means through the neutron bombardment of plutonium 239 and published this work in 1954 with the disclaimer that it was not the first studies that had been carried out on those elements 53 54 The Ivy Mike studies were declassified and published in 1955 52 The first significant submicrograms amounts of einsteinium were produced in 1961 by Cunningham and colleagues but this has not been done for fermium yet 55 The first isotope of mendelevium 256Md half life 87 min was synthesized by Albert Ghiorso Glenn T Seaborg Gregory R Choppin Bernard G Harvey and Stanley G Thompson when they bombarded an 253Es target with alpha particles in the 60 inch cyclotron of Berkeley Radiation Laboratory this was the first isotope of any element to be synthesized one atom at a time 56 There were several attempts to obtain isotopes of nobelium by Swedish 1957 and American 1958 groups but the first reliable result was the synthesis of 256No by the Russian group Georgy Flyorov et al in 1965 as acknowledged by the IUPAC in 1992 In their experiments Flyorov et al bombarded uranium 238 with neon 22 10 In 1961 Ghiorso et al obtained the first isotope of lawrencium by irradiating californium mostly californium 252 with boron 10 and boron 11 ions 10 The mass number of this isotope was not clearly established possibly 258 or 259 at the time In 1965 256Lr was synthesized by Flyorov et al from 243Am and 18O Thus IUPAC recognized the nuclear physics teams at Dubna and Berkeley as the co discoverers of lawrencium Isotopes EditNuclear properties of isotopes of the most important transplutonium isotopes 57 58 59 Isotope Half life Probability of spontaneousfission in Emission energy MeV yield in Specific activity Bq kg notes 2 ofa g a b particles fission241Am 432 2 7 y 4 3 18 10 10 5 485 84 8 5 442 13 1 5 388 1 66 0 059 35 9 0 026 2 27 1 27 1014 546 1243Am 7 37 4 103 y 3 7 2 10 9 5 275 87 1 5 233 11 2 5 181 1 36 0 074 67 2 0 043 5 9 7 39 1012 273 3242Cm 162 8 2 d 6 2 3 10 6 6 069 25 92 6 112 74 08 0 044 0 04 0 102 4 10 3 1 23 1017 7 6 109244Cm 18 10 2 y 1 37 3 10 4 5 762 23 6 5 804 76 4 0 043 0 02 0 100 1 5 10 3 2 96 1015 4 1 109245Cm 8 5 1 103 y 6 1 9 10 7 5 529 0 58 5 488 0 83 5 361 93 2 0 175 9 88 0 133 2 83 6 35 1012 3 9 104246Cm 4 76 4 103 y 0 02615 7 5 343 17 8 5 386 82 2 0 045 19 1 13 1013 2 95 109247Cm 1 56 5 107 y 5 267 13 8 5 212 5 7 5 147 1 2 0 402 72 0 278 3 4 3 43 109 248Cm 3 48 6 105 y 8 39 16 5 034 16 52 5 078 75 1 40 1011 1 29 1010249Bk 330 4 d 4 7 2 10 8 5 406 1 10 3 5 378 2 6 10 4 0 32 5 8 10 5 5 88 1016 2 76 107249Cf 351 2 y 5 0 4 10 7 6 193 2 46 6 139 1 33 5 946 3 33 0 388 66 0 333 14 6 1 51 1014 7 57 105250Cf 13 08 9 y 0 077 3 5 988 14 99 6 030 84 6 0 043 4 04 1015 3 11 1012251Cf 900 40 y 6 078 2 6 5 567 0 9 5 569 0 9 0 177 17 3 0 227 6 8 5 86 1013 252Cf 2 645 8 y 3 092 8 6 075 15 2 6 118 81 6 0 042 1 4 10 2 0 100 1 3 10 2 1 92 1016 6 14 1014254Cf 60 5 2 d 100 5 834 0 26 5 792 5 3 10 2 9 75 1014 3 13 1017253Es 20 47 3 d 8 7 3 10 6 6 540 0 85 6 552 0 71 6 590 6 6 0 387 0 05 0 429 8 10 3 9 33 1017 8 12 1010254Es 275 7 5 d lt 3 10 6 6 347 0 75 6 358 2 6 6 415 1 8 0 042 100 0 034 30 6 9 1016 255Es 39 8 12 d 0 0041 2 6 267 0 78 6 401 7 4 38 1017 b 3 81 1016 a 1 95 1013255Fm 20 07 7 h 2 4 10 10 5 7 022 93 4 6 963 5 04 6 892 0 62 0 00057 19 1 0 081 1 2 27 1019 5 44 1012256Fm 157 6 13 min 91 9 3 6 872 1 2 6 917 6 9 1 58 1020 1 4 1019257Fm 100 5 2 d 0 210 4 6 752 0 58 6 695 3 39 6 622 0 6 0 241 11 0 179 8 7 1 87 1017 3 93 1014256Md 77 2 min 7 142 1 84 7 206 5 9 3 53 1020 257Md 5 52 5 h 7 074 14 0 371 11 7 0 325 2 5 8 17 1019 258Md 51 5 3 d 6 73 3 64 1017 255No 3 1 2 min 8 312 1 16 8 266 2 6 8 121 27 8 0 187 3 4 8 78 1021 259No 58 5 min 7 455 9 8 7 500 29 3 7 533 17 3 4 63 1020 256Lr 27 3 s lt 0 03 8 319 5 4 8 390 16 8 430 33 5 96 1022 257Lr 646 25 ms 8 796 18 8 861 82 1 54 1024 nbsp Actinides have 89 103 protons and usually 117 159 neutrons 32 isotopes of actinium and eight excited isomeric states of some of its nuclides were identified by 2016 57 Three isotopes 225Ac 227Ac and 228Ac were found in nature and the others were produced in the laboratory only the three natural isotopes are used in applications Actinium 225 is a member of the radioactive neptunium series 60 it was first discovered in 1947 as a decay product of uranium 233 it is an a emitter with a half life of 10 days Actinium 225 is less available than actinium 228 but is more promising in radiotracer applications 30 Actinium 227 half life 21 77 years occurs in all uranium ores but in small quantities One gram of uranium in radioactive equilibrium contains only 2 10 10 gram of 227Ac 30 57 Actinium 228 is a member of the radioactive thorium series formed by the decay of 228Ra 60 it is a b emitter with a half life of 6 15 hours In one tonne of thorium there is 5 10 8 gram of 228Ac It was discovered by Otto Hahn in 1906 30 There are 31 known isotopes of thorium ranging in mass number from 208 to 238 57 Of these the longest lived is 232Th whose half life of 1 4 1010 years means that it still exists in nature as a primordial nuclide The next longest lived is 230Th an intermediate decay product of 238U with a half life of 75 400 years Several other thorium isotopes have half lives over a day all of these are also transient in the decay chains of 232Th 235U and 238U 28 isotopes of protactinium are known with mass numbers 212 239 57 as well as three excited isomeric states Only 231Pa and 234Pa have been found in nature All the isotopes have short lifetimes except for protactinium 231 half life 32 760 years The most important isotopes are 231Pa and 233Pa which is an intermediate product in obtaining uranium 233 and is the most affordable among artificial isotopes of protactinium 233Pa has convenient half life and energy of g radiation and thus was used in most studies of protactinium chemistry Protactinium 233 is a b emitter with a half life of 26 97 days 57 61 There are 26 known isotopes of uranium having mass numbers 215 242 except 220 and 241 58 Three of them 234U 235U and 238U are present in appreciable quantities in nature Among others the most important is 233U which is a final product of transformation of 232Th irradiated by slow neutrons 233U has a much higher fission efficiency by low energy thermal neutrons compared e g with 235U Most uranium chemistry studies were carried out on uranium 238 owing to its long half life of 4 4 109 years 62 There are 24 isotopes of neptunium with mass numbers of 219 220 and 223 244 58 they are all highly radioactive The most popular among scientists are long lived 237Np t1 2 2 20 106 years and short lived 239Np 238Np t1 2 2 days 38 There are 20 known isotopes of plutonium having mass numbers 228 247 58 The most stable isotope of plutonium is 244Pu with half life of 8 13 107 years 63 Eighteen isotopes of americium are known with mass numbers from 229 to 247 with the exception of 231 58 The most important are 241Am and 243Am which are alpha emitters and also emit soft but intense g rays both of them can be obtained in an isotopically pure form Chemical properties of americium were first studied with 241Am but later shifted to 243Am which is almost 20 times less radioactive The disadvantage of 243Am is production of the short lived daughter isotope 239Np which has to be considered in the data analysis 64 Among 19 isotopes of curium ranging in mass number from 233 to 251 58 the most accessible are 242Cm and 244Cm they are a emitters but with much shorter lifetime than the americium isotopes These isotopes emit almost no g radiation but undergo spontaneous fission with the associated emission of neutrons More long lived isotopes of curium 245 248Cm all a emitters are formed as a mixture during neutron irradiation of plutonium or americium Upon short irradiation this mixture is dominated by 246Cm and then 248Cm begins to accumulate Both of these isotopes especially 248Cm have a longer half life 3 48 105 years and are much more convenient for carrying out chemical research than 242Cm and 244Cm but they also have a rather high rate of spontaneous fission 247Cm has the longest lifetime among isotopes of curium 1 56 107 years but is not formed in large quantities because of the strong fission induced by thermal neutrons Seventeen isotopes of berkelium were identified with mass numbers 233 234 236 238 and 240 252 58 Only 249Bk is available in large quantities it has a relatively short half life of 330 days and emits mostly soft b particles which are inconvenient for detection Its alpha radiation is rather weak 1 45 10 3 with respect to b radiation but is sometimes used to detect this isotope 247Bk is an alpha emitter with a long half life of 1 380 years but it is hard to obtain in appreciable quantities it is not formed upon neutron irradiation of plutonium because of the b stability of isotopes of curium isotopes with mass number below 248 64 The 20 isotopes of californium with mass numbers 237 256 are formed in nuclear reactors 58 californium 253 is a b emitter and the rest are a emitters The isotopes with even mass numbers 250Cf 252Cf and 254Cf have a high rate of spontaneous fission especially 254Cf of which 99 7 decays by spontaneous fission Californium 249 has a relatively long half life 352 years weak spontaneous fission and strong g emission that facilitates its identification 249Cf is not formed in large quantities in a nuclear reactor because of the slow b decay of the parent isotope 249Bk and a large cross section of interaction with neutrons but it can be accumulated in the isotopically pure form as the b decay product of pre selected 249Bk Californium produced by reactor irradiation of plutonium mostly consists of 250Cf and 252Cf the latter being predominant for large neutron fluences and its study is hindered by the strong neutron radiation 65 Properties of some transplutonium isotope pairs 66 Parent isotope t1 2 Daughter isotope t1 2 Time to establish radioactive equilibrium243Am 7370 years 239Np 2 35 days 47 3 days245Cm 8265 years 241Pu 14 years 129 years247Cm 1 64 107 years 243Pu 4 95 hours 7 2 days254Es 270 days 250Bk 3 2 hours 35 2 hours255Es 39 8 days 255Fm 22 hours 5 days257Fm 79 days 253Cf 17 6 days 49 daysAmong the 18 known isotopes of einsteinium with mass numbers from 240 to 257 58 the most affordable is 253Es It is an a emitter with a half life of 20 47 days a relatively weak g emission and small spontaneous fission rate as compared with the isotopes of californium Prolonged neutron irradiation also produces a long lived isotope 254Es t1 2 275 5 days 65 Twenty isotopes of fermium are known with mass numbers of 241 260 254Fm 255Fm and 256Fm are a emitters with a short half life hours which can be isolated in significant amounts 257Fm t1 2 100 days can accumulate upon prolonged and strong irradiation All these isotopes are characterized by high rates of spontaneous fission 65 67 Among the 17 known isotopes of mendelevium mass numbers from 244 to 260 58 the most studied is 256Md which mainly decays through the electron capture a radiation is 10 with the half life of 77 minutes Another alpha emitter 258Md has a half life of 53 days Both these isotopes are produced from rare einsteinium 253Es and 255Es respectively that therefore limits their availability 57 Long lived isotopes of nobelium and isotopes of lawrencium and of heavier elements have relatively short half lives For nobelium 11 isotopes are known with mass numbers 250 260 and 262 The chemical properties of nobelium and lawrencium were studied with 255No t1 2 3 min and 256Lr t1 2 35 s The longest lived nobelium isotope 259No has a half life of approximately 1 hour 57 Lawrencium has 13 known isotopes with mass numbers 251 262 and 266 The most stable of them all is 266Lr with a half life of 11 hours Among all of these the only isotopes that occur in sufficient quantities in nature to be detected in anything more than traces and have a measurable contribution to the atomic weights of the actinides are the primordial 232Th 235U and 238U and three long lived decay products of natural uranium 230Th 231Pa and 234U Natural thorium consists of 0 02 2 230Th and 99 98 2 232Th natural protactinium consists of 100 231Pa and natural uranium consists of 0 0054 5 234U 0 7204 6 235U and 99 2742 10 238U 68 Formation in nuclear reactors Edit nbsp Table of nuclides Buildup of actinides in a nuclear reactor including radioative decayThe figure buildup of actinides is a table of nuclides with the number of neutrons on the horizontal axis isotopes and the number of protons on the vertical axis elements The red dot divides the nuclides in two groups so the figure is more compact Each nuclide is represented by a square with the mass number of the element and its half life 69 Naturally existing actinide isotopes Th U are marked with a bold border alpha emitters have a yellow colour and beta emitters have a blue colour Pink indicates electron capture 236Np whereas white stands for a long lasting metastable state 242Am The formation of actinide nuclides is primarily characterised by 70 Neutron capture reactions n g which are represented in the figure by a short right arrow The n 2n reactions and the less frequently occurring g n reactions are also taken into account both of which are marked by a short left arrow Even more rarely and only triggered by fast neutrons the n 3n reaction occurs which is represented in the figure with one example marked by a long left arrow In addition to these neutron or gamma induced nuclear reactions the radioactive conversion of actinide nuclides also affects the nuclide inventory in a reactor These decay types are marked in the figure by diagonal arrows The beta minus decay marked with an arrow pointing up left plays a major role for the balance of the particle densities of the nuclides Nuclides decaying by positron emission beta plus decay or electron capture ϵ do not occur in a nuclear reactor except as products of knockout reactions their decays are marked with arrows pointing down right Due to the long half lives of the given nuclides alpha decay plays almost no role in the formation and decay of the actinides in a power reactor as the residence time of the nuclear fuel in the reactor core is rather short a few years Exceptions are the two relatively short lived nuclides 242Cm T1 2 163 d and 236Pu T1 2 2 9 y Only for these two cases the a decay is marked on the nuclide map by a long arrow pointing down left A few long lived actinide isotopes such as 244Pu and 250Cm cannot be produced in reactors because neutron capture does not happen quickly enough to bypass the short lived beta decaying nuclides 243Pu and 249Cm they can however be generated in nuclear explosions which have much higher neutron fluxes Distribution in nature Edit nbsp Unprocessed uranium oreThorium and uranium are the most abundant actinides in nature with the respective mass concentrations of 16 ppm and 4 ppm 71 Uranium mostly occurs in the Earth s crust as a mixture of its oxides in the mineral uraninite which is also called pitchblende because of its black color There are several dozens of other uranium minerals such as carnotite KUO2VO4 3H2O and autunite Ca UO2 2 PO4 2 nH2O The isotopic composition of natural uranium is 238U relative abundance 99 2742 235U 0 7204 and 234U 0 0054 of these 238U has the largest half life of 4 51 109 years 72 73 The worldwide production of uranium in 2009 amounted to 50 572 tonnes of which 27 3 was mined in Kazakhstan Other important uranium mining countries are Canada 20 1 Australia 15 7 Namibia 9 1 Russia 7 0 and Niger 6 4 74 Content of plutonium in uranium and thorium ores 75 Ore Location Uranium content Mass ratio 239Pu ore Ratio 239Pu U 1012 Uraninite Canada 13 5 9 1 10 12 7 1Uraninite Congo 38 4 8 10 12 12Uraninite Colorado US 50 3 8 10 12 7 7Monazite Brazil 0 24 2 1 10 14 8 3Monazite North Carolina US 1 64 5 9 10 14 3 6Fergusonite 0 25 lt 1 10 14 lt 4Carnotite 10 lt 4 10 14 lt 0 4The most abundant thorium minerals are thorianite ThO2 thorite ThSiO4 and monazite Th Ca Ce PO4 Most thorium minerals contain uranium and vice versa and they all have significant fraction of lanthanides Rich deposits of thorium minerals are located in the United States 440 000 tonnes Australia and India 300 000 tonnes each and Canada 100 000 tonnes 76 The abundance of actinium in the Earth s crust is only about 5 10 15 61 Actinium is mostly present in uranium containing but also in other minerals though in much smaller quantities The content of actinium in most natural objects corresponds to the isotopic equilibrium of parent isotope 235U and it is not affected by the weak Ac migration 30 Protactinium is more abundant 10 12 in the Earth s crust than actinium It was discovered in the uranium ore in 1913 by Fajans and Gohring 34 As actinium the distribution of protactinium follows that of 235U 61 The half life of the longest lived isotope of neptunium 237Np is negligible compared to the age of the Earth Thus neptunium is present in nature in negligible amounts produced as intermediate decay products of other isotopes 38 Traces of plutonium in uranium minerals were first found in 1942 and the more systematic results on 239Pu are summarized in the table no other plutonium isotopes could be detected in those samples The upper limit of abundance of the longest living isotope of plutonium 244Pu is 3 10 20 Plutonium could not be detected in samples of lunar soil Owing to its scarcity in nature most plutonium is produced synthetically 75 Extraction Edit nbsp Monazite a major thorium mineralOwing to the low abundance of actinides their extraction is a complex multistep process Fluorides of actinides are usually used because they are insoluble in water and can be easily separated with redox reactions Fluorides are reduced with calcium magnesium or barium 77 2 AmF 3 3 Ba 1150 1350 C 3 BaF 2 2 Am PuF 4 2 Ba 1200 C 2 BaF 2 Pu UF 4 2 Mg gt 500 C U 2 MgF 2 displaystyle begin array l ce 2AmF3 3Ba gt ce 1150 1350 circ C 3BaF2 2Am ce PuF4 2Ba gt ce 1200 circ C 2BaF2 Pu ce UF4 2Mg gt ce gt 500 circ C U 2MgF2 end array nbsp Among the actinides thorium and uranium are the easiest to isolate Thorium is extracted mostly from monazite thorium pyrophosphate ThP2O7 is reacted with nitric acid and the produced thorium nitrate treated with tributyl phosphate Rare earth impurities are separated by increasing the pH in sulfate solution 77 In another extraction method monazite is decomposed with a 45 aqueous solution of sodium hydroxide at 140 C Mixed metal hydroxides are extracted first filtered at 80 C washed with water and dissolved with concentrated hydrochloric acid Next the acidic solution is neutralized with hydroxides to pH 5 8 that results in precipitation of thorium hydroxide Th OH 4 contaminated with 3 of rare earth hydroxides the rest of rare earth hydroxides remains in solution Thorium hydroxide is dissolved in an inorganic acid and then purified from the rare earth elements An efficient method is the dissolution of thorium hydroxide in nitric acid because the resulting solution can be purified by extraction with organic solvents 77 nbsp Separation of uranium and plutonium from spent nuclear fuel using the PUREX process 78 Th OH 4 4 HNO3 Th NO3 4 4 H2OMetallic thorium is separated from the anhydrous oxide chloride or fluoride by reacting it with calcium in an inert atmosphere 79 ThO2 2 Ca 2 CaO ThSometimes thorium is extracted by electrolysis of a fluoride in a mixture of sodium and potassium chloride at 700 800 C in a graphite crucible Highly pure thorium can be extracted from its iodide with the crystal bar process 80 Uranium is extracted from its ores in various ways In one method the ore is burned and then reacted with nitric acid to convert uranium into a dissolved state Treating the solution with a solution of tributyl phosphate TBP in kerosene transforms uranium into an organic form UO2 NO3 2 TBP 2 The insoluble impurities are filtered and the uranium is extracted by reaction with hydroxides as NH4 2U2O7 or with hydrogen peroxide as UO4 2H2O 77 When the uranium ore is rich in such minerals as dolomite magnesite etc those minerals consume much acid In this case the carbonate method is used for uranium extraction Its main component is an aqueous solution of sodium carbonate which converts uranium into a complex UO2 CO3 3 4 which is stable in aqueous solutions at low concentrations of hydroxide ions The advantages of the sodium carbonate method are that the chemicals have low corrosivity compared to nitrates and that most non uranium metals precipitate from the solution The disadvantage is that tetravalent uranium compounds precipitate as well Therefore the uranium ore is treated with sodium carbonate at elevated temperature and under oxygen pressure 2 UO2 O2 6 CO2 3 2 UO2 CO3 3 4 This equation suggests that the best solvent for the uranium carbonate processing is a mixture of carbonate with bicarbonate At high pH this results in precipitation of diuranate which is treated with hydrogen in the presence of nickel yielding an insoluble uranium tetracarbonate 77 Another separation method uses polymeric resins as a polyelectrolyte Ion exchange processes in the resins result in separation of uranium Uranium from resins is washed with a solution of ammonium nitrate or nitric acid that yields uranyl nitrate UO2 NO3 2 6H2O When heated it turns into UO3 which is converted to UO2 with hydrogen UO3 H2 UO2 H2OReacting uranium dioxide with hydrofluoric acid changes it to uranium tetrafluoride which yields uranium metal upon reaction with magnesium metal 79 4 HF UO2 UF4 2 H2OTo extract plutonium neutron irradiated uranium is dissolved in nitric acid and a reducing agent FeSO4 or H2O2 is added to the resulting solution This addition changes the oxidation state of plutonium from 6 to 4 while uranium remains in the form of uranyl nitrate UO2 NO3 2 The solution is treated with a reducing agent and neutralized with ammonium carbonate to pH 8 that results in precipitation of Pu4 compounds 77 In another method Pu4 and UO2 2 are first extracted with tributyl phosphate then reacted with hydrazine washing out the recovered plutonium 77 The major difficulty in separation of actinium is the similarity of its properties with those of lanthanum Thus actinium is either synthesized in nuclear reactions from isotopes of radium or separated using ion exchange procedures 30 Properties EditActinides have similar properties to lanthanides The 6d and 7s electronic shells are filled in actinium and thorium and the 5f shell is being filled with further increase in atomic number the 4f shell is filled in the lanthanides The first experimental evidence for the filling of the 5f shell in actinides was obtained by McMillan and Abelson in 1940 81 As in lanthanides see lanthanide contraction the ionic radius of actinides monotonically decreases with atomic number see also Aufbau principle 82 Properties of actinides the mass of the most long lived isotope is in square brackets 73 83 Element Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No LrCore charge Z 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103atomic mass 227 232 0377 4 231 03588 2 238 02891 3 237 244 243 247 247 251 252 257 258 259 266 Number of natural isotopes 84 3 7 3 8 3 4 0 0 0 0 0 0 0 0 0Natural isotopes 84 85 225 227 228 227 232 234 231 233 234 233 240 237 239 240 238 240 244 Natural quantity isotopes 230 232 231 234 235 238 Longest lived isotope 227 232 231 238 237 244 243 247 247 251 252 257 258 259 266Half life of the longest lived isotope 21 8 years 14 billion years 32 500 years 4 47 billion years 2 14 million years 80 8 million years 7 370 years 15 6 million years 1 380 years 900 years 1 29 years 100 5 days 52 days 58 min 11 hoursMost common isotope 227 232 231 238 237 239 241 244 249 252 253 255 256 255 260Half life of the most common isotope 21 8 years 14 billion years 32 500 years 4 47 billion years 2 14 million years 24 100 years 433 years 18 1 years 320 days 2 64 years 20 47 days 20 07 hours 78 min 3 1 min 2 7 minElectronic configuration inthe ground state gas phase 6d17s2 6d27s2 5f26d17s2 5f36d17s2 5f46d17s2 5f67s2 5f77s2 5f76d17s2 5f97s2 5f107s2 5f117s2 5f127s2 5f137s2 5f147s2 5f147s27p1Oxidation states 2 3 2 3 4 2 3 4 5 2 3 4 5 6 3 4 5 6 7 3 4 5 6 7 2 3 4 5 6 7 2 3 4 6 2 3 4 2 3 4 2 3 4 2 3 2 3 2 3 3Metallic radius nm 0 203 0 180 0 162 0 153 0 150 0 162 0 173 0 174 0 170 0 186 0 186 0 198 0 194 0 197 0 171Ionic radius nm An4 An3 0 126 0 114 0 104 0 118 0 103 0 118 0 101 0 116 0 100 0 115 0 099 0 114 0 099 0 112 0 097 0 110 0 096 0 109 0 085 0 098 0 084 0 091 0 084 0 090 0 084 0 095 0 083 0 088Temperature C melting boiling 10503198 18424788 1568 4027 1132 24131 639 4174 639 43228 1176 2607 13403110 9862627 900 1470 860 996 1530 830 830 1630 Density g cm3 10 07 11 78 15 37 19 06 20 45 19 84 11 7 13 51 14 78 15 1 8 84 9 7 10 3 9 9 14 4Standard electrode potential V E An4 An0 E An3 An0 2 13 1 83 1 47 1 38 1 66 1 30 1 79 1 25 2 00 0 90 2 07 0 75 2 06 0 55 1 96 0 59 1 97 0 36 1 98 0 29 1 96 1 74 1 20 2 10Color M H2O n 4 M H2O n 3 Colorless Colorless Blue Yellow Dark blue Green Purple Yellow green Purple Brown Violet Red Rose Yellow Colorless BeigeYellow green Green Green Pink Approximate colors of actinide ions in aqueous solutionColors for the actinides 100 103 are unknown as sufficient quantities have not yet been synthesized The colour of CmO2 2 was likewise not recorded 86 87 Actinide Z 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103Oxidation state 2 Fm2 Md2 No2 3 Ac3 Th3 Pa3 U3 Np3 Pu3 Am3 Cm3 Bk3 Cf3 Es3 Fm3 Md3 No3 Lr3 4 Th4 Pa4 U4 Np4 Pu4 Am4 Cm4 Bk4 Cf4 5 PaO 2 UO 2 NpO 2 PuO 2 AmO 2 6 UO2 2 NpO2 2 PuO2 2 AmO2 2 CmO2 2 7 NpO3 2 PuO3 2 AmO3 5Physical properties Edit nbsp nbsp Major crystal structures of some actinides vs temperature Metallic and ionic radii of actinides 83 nbsp A pellet of 238PuO2 to be used in a radioisotope thermoelectric generator for either the Cassini or Galileo mission The pellet produces 62 watts of heat and glows because of the heat generated by the radioactive decay primarily a Photo is taken after insulating the pellet under a graphite blanket for minutes and removing the blanket nbsp CaliforniumActinides are typical metals All of them are soft and have a silvery color but tarnish in air 88 relatively high density and plasticity Some of them can be cut with a knife Their electrical resistivity varies between 15 and 150 µW cm 83 The hardness of thorium is similar to that of soft steel so heated pure thorium can be rolled in sheets and pulled into wire Thorium is nearly half as dense as uranium and plutonium but is harder than either of them All actinides are radioactive paramagnetic and with the exception of actinium have several crystalline phases plutonium has seven and uranium neptunium and californium three The crystal structures of protactinium uranium neptunium and plutonium do not have clear analogs among the lanthanides and are more similar to those of the 3d transition metals 73 All actinides are pyrophoric especially when finely divided that is they spontaneously ignite upon reaction with air at room temperature 88 89 The melting point of actinides does not have a clear dependence on the number of f electrons The unusually low melting point of neptunium and plutonium 640 C is explained by hybridization of 5f and 6d orbitals and the formation of directional bonds in these metals 73 Comparison of ionic radii of lanthanides and actinides 90 Lanthanides Ln3 A Actinides An3 A An4 ALanthanum 1 061 Actinium 1 11 Cerium 1 034 Thorium 1 08 0 99Praseodymium 1 013 Protactinium 1 05 0 93Neodymium 0 995 Uranium 1 03 0 93Promethium 0 979 Neptunium 1 01 0 92Samarium 0 964 Plutonium 1 00 0 90Europium 0 950 Americium 0 99 0 89Gadolinium 0 938 Curium 0 98 0 88Terbium 0 923 Berkelium Dysprosium 0 908 Californium Holmium 0 894 Einsteinium Erbium 0 881 Fermium Thulium 0 869 Mendelevium Ytterbium 0 858 Nobelium Lutetium 0 848 Lawrencium Chemical properties Edit Like the lanthanides all actinides are highly reactive with halogens and chalcogens however the actinides react more easily Actinides especially those with a small number of 5f electrons are prone to hybridization This is explained by the similarity of the electron energies at the 5f 7s and 6d shells Most actinides exhibit a larger variety of valence states and the most stable are 6 for uranium 5 for protactinium and neptunium 4 for thorium and plutonium and 3 for actinium and other actinides 91 Actinium is chemically similar to lanthanum which is explained by their similar ionic radii and electronic structures Like lanthanum actinium almost always has an oxidation state of 3 in compounds but it is less reactive and has more pronounced basic properties Among other trivalent actinides Ac3 is least acidic i e has the weakest tendency to hydrolyze in aqueous solutions 30 73 Thorium is rather active chemically Owing to lack of electrons on 6d and 5f orbitals the tetravalent thorium compounds are colorless At pH lt 3 the solutions of thorium salts are dominated by the cations Th H2O 8 4 The Th4 ion is relatively large and depending on the coordination number can have a radius between 0 95 and 1 14 A As a result thorium salts have a weak tendency to hydrolyse The distinctive ability of thorium salts is their high solubility both in water and polar organic solvents 73 Protactinium exhibits two valence states the 5 is stable and the 4 state easily oxidizes to protactinium V Thus tetravalent protactinium in solutions is obtained by the action of strong reducing agents in a hydrogen atmosphere Tetravalent protactinium is chemically similar to uranium IV and thorium IV Fluorides phosphates hypophosphate iodate and phenylarsonates of protactinium IV are insoluble in water and dilute acids Protactinium forms soluble carbonates The hydrolytic properties of pentavalent protactinium are close to those of tantalum V and niobium V The complex chemical behavior of protactinium is a consequence of the start of the filling of the 5f shell in this element 61 Uranium has a valence from 3 to 6 the last being most stable In the hexavalent state uranium is very similar to the group 6 elements Many compounds of uranium IV and uranium VI are non stoichiometric i e have variable composition For example the actual chemical formula of uranium dioxide is UO2 x where x varies between 0 4 and 0 32 Uranium VI compounds are weak oxidants Most of them contain the linear uranyl group UO2 2 Between 4 and 6 ligands can be accommodated in an equatorial plane perpendicular to the uranyl group The uranyl group acts as a hard acid and forms stronger complexes with oxygen donor ligands than with nitrogen donor ligands NpO2 2 and PuO2 2 are also the common form of Np and Pu in the 6 oxidation state Uranium IV compounds exhibit reducing properties e g they are easily oxidized by atmospheric oxygen Uranium III is a very strong reducing agent Owing to the presence of d shell uranium as well as many other actinides forms organometallic compounds such as UIII C5H5 3 and UIV C5H5 4 73 92 Neptunium has valence states from 3 to 7 which can be simultaneously observed in solutions The most stable state in solution is 5 but the valence 4 is preferred in solid neptunium compounds Neptunium metal is very reactive Ions of neptunium are prone to hydrolysis and formation of coordination compounds 38 Plutonium also exhibits valence states between 3 and 7 inclusive and thus is chemically similar to neptunium and uranium It is highly reactive and quickly forms an oxide film in air Plutonium reacts with hydrogen even at temperatures as low as 25 50 C it also easily forms halides and intermetallic compounds Hydrolysis reactions of plutonium ions of different oxidation states are quite diverse Plutonium V can enter polymerization reactions 93 94 The largest chemical diversity among actinides is observed in americium which can have valence between 2 and 6 Divalent americium is obtained only in dry compounds and non aqueous solutions acetonitrile Oxidation states 3 5 and 6 are typical for aqueous solutions but also in the solid state Tetravalent americium forms stable solid compounds dioxide fluoride and hydroxide as well as complexes in aqueous solutions It was reported that in alkaline solution americium can be oxidized to the heptavalent state but these data proved erroneous The most stable valence of americium is 3 in the aqueous solutions and 3 or 4 in solid compounds 95 Valence 3 is dominant in all subsequent elements up to lawrencium with the exception of nobelium Curium can be tetravalent in solids fluoride dioxide Berkelium along with a valence of 3 also shows the valence of 4 more stable than that of curium the valence 4 is observed in solid fluoride and dioxide The stability of Bk4 in aqueous solution is close to that of Ce4 96 Only valence 3 was observed for californium einsteinium and fermium The divalent state is proven for mendelevium and nobelium and in nobelium it is more stable than the trivalent state Lawrencium shows valence 3 both in solutions and solids 95 The redox potential E M 4 AnO 2 2 displaystyle ce mathit E frac M 4 AnO2 2 nbsp increases from 0 32 V in uranium through 0 34 V Np and 1 04 V Pu to 1 34 V in americium revealing the increasing reduction ability of the An4 ion from americium to uranium All actinides form AnH3 hydrides of black color with salt like properties Actinides also produce carbides with the general formula of AnC or AnC2 U2C3 for uranium as well as sulfides An2S3 and AnS2 91 nbsp Uranyl nitrate UO2 NO3 2 nbsp Aqueous solutions of uranium III IV V VI salts nbsp Aqueous solutions of neptunium III IV V VI VII salts nbsp Aqueous solutions of plutonium III IV V VI VII salts nbsp Uranium tetrachloride nbsp Uranium hexafluoride nbsp U3O8 yellowcake Compounds EditOxides and hydroxides Edit Oxides of actinides 30 38 61 97 98 Compound Color Crystal symmetry type Lattice constants A Density g cm3 Temperature Ca b cAc2O3 White Hexagonal La2O3 4 07 6 29 9 19 PaO2 Cubic CaF2 5 505 Pa2O5 White cubic CaF2 Cubic Tetragonal Hexagonal Rhombohedral Orthorhombic 5 446 10 891 5 429 3 817 5 425 6 92 4 02 10 992 5 503 13 22 4 18 700 700 1100 1000 1000 1200 1240 1400 ThO2 Colorless Cubic 5 59 9 87 UO2 Black brown Cubic 5 47 10 9 NpO2 Greenish brown Cubic CaF2 5 424 11 1 PuO Black Cubic NaCl 4 96 13 9 PuO2 Olive green Cubic 5 39 11 44 Am2O3 Red brown Red brown Cubic Mn2O3 Hexagonal La2O3 11 03 3 817 5 971 10 57 11 7 AmO2 Black Cubic CaF2 5 376 Cm2O3 White 99 Cubic Mn2O2 Hexagonal LaCl3 Monoclinic Sm2O3 11 01 3 80 14 28 3 65 6 8 9 11 7 CmO2 Black Cubic CaF2 5 37 Bk2O3 Light brown Cubic Mn2O3 10 886 BkO2 Red brown Cubic CaF2 5 33 Cf2O3 100 Colorless Yellowish Cubic Mn2O3 Monoclinic Sm2O3 Hexagonal La2O3 10 79 14 12 3 72 3 59 8 80 5 96 CfO2 Black Cubic 5 31 Es2O3 Cubic Mn2O3 Monoclinic Hexagonal La2O3 10 07 14 1 3 7 3 59 8 80 6 Approximate colors of actinide oxides most stable are bolded 101 Oxidation state 89 90 91 92 93 94 95 96 97 98 99 3 Ac2O3 Pu2O3 Am2O3 Cm2O3 Bk2O3 Cf2O3 Es2O3 4 ThO2 PaO2 UO2 NpO2 PuO2 AmO2 CmO2 BkO2 CfO2 5 Pa2O5 U2O5 Np2O5 5 6 U3O8 6 UO3Dioxides of some actinides Chemical formula ThO2 PaO2 UO2 NpO2 PuO2 AmO2 CmO2 BkO2 CfO2CAS number 1314 20 1 12036 03 2 1344 57 6 12035 79 9 12059 95 9 12005 67 3 12016 67 0 12010 84 3 12015 10 0Molar mass 264 04 263 035 270 03 269 047 276 063 275 06 270 284 279 069 283 078Melting point 102 3390 C 2865 C 2547 C 2400 C 2175 CCrystal structure nbsp An4 O2 Space group Fm3 mCoordination number An 8 O 4 An actinide Depending on the isotopesSome actinides can exist in several oxide forms such as An2O3 AnO2 An2O5 and AnO3 For all actinides oxides AnO3 are amphoteric and An2O3 AnO2 and An2O5 are basic they easily react with water forming bases 91 An2O3 3 H2O 2 An OH 3 These bases are poorly soluble in water and by their activity are close to the hydroxides of rare earth metals 91 Np OH 3 has not yet been synthesized Pu OH 3 has a blue color while Am OH 3 is pink and curium hydroxide Cm OH 3 is colorless 103 Bk OH 3 and Cf OH 3 are also known as are tetravalent hydroxides for Np Pu and Am and pentavalent for Np and Am 103 The strongest base is of actinium All compounds of actinium are colorless except for black actinium sulfide Ac2S3 91 Dioxides of tetravalent actinides crystallize in the cubic system same as in calcium fluoride Thorium reacting with oxygen exclusively forms the dioxide Th O 2 1000 C ThO 2 Thorium dioxide displaystyle ce Th O2 gt ce 1000 circ C overbrace ThO2 Thorium dioxide nbsp Thorium dioxide is a refractory material with the highest melting point among any known oxide 3390 C 101 Adding 0 8 1 ThO2 to tungsten stabilizes its structure so the doped filaments have better mechanical stability to vibrations To dissolve ThO2 in acids it is heated to 500 600 C heating above 600 C produces a very resistant to acids and other reagents form of ThO2 Small addition of fluoride ions catalyses dissolution of thorium dioxide in acids Two protactinium oxides have been obtained PaO2 black and Pa2O5 white the former is isomorphic with ThO2 and the latter is easier to obtain Both oxides are basic and Pa OH 5 is a weak poorly soluble base 91 Decomposition of certain salts of uranium for example UO2 NO3 6H2O in air at 400 C yields orange or yellow UO3 101 This oxide is amphoteric and forms several hydroxides the most stable being uranyl hydroxide UO2 OH 2 Reaction of uranium VI oxide with hydrogen results in uranium dioxide which is similar in its properties with ThO2 This oxide is also basic and corresponds to the uranium hydroxide U OH 4 91 Plutonium neptunium and americium form two basic oxides An2O3 and AnO2 Neptunium trioxide is unstable thus only Np3O8 could be obtained so far However the oxides of plutonium and neptunium with the chemical formula AnO2 and An2O3 are well characterized 91 Salts Edit Trichlorides of some actinides 104 Chemical formula AcCl3 UCl3 NpCl3 PuCl3 AmCl3 CmCl3 BkCl3 CfCl3CAS number 22986 54 5 10025 93 1 20737 06 8 13569 62 5 13464 46 5 13537 20 7 13536 46 4 13536 90 8Molar mass 333 386 344 387 343 406 350 32 349 42 344 358 353 428 357 438Melting point 837 C 800 C 767 C 715 C 695 C 603 C 545 CBoiling point 1657 C 1767 C 850 CCrystal structure nbsp An3 Cl Space group P63 mCoordination number An 9 Cl 3 Lattice constants a 762 pm c 455 pm a 745 2 pm c 432 8 pm a 739 4 pm c 424 3 pm a 738 2 pm c 421 4 pm a 726 pm c 414 pm a 738 2 pm c 412 7 pm a 738 pm c 409 pm An actinide Depending on the isotopesActinide fluorides 38 61 98 104 105 Compound Color Crystal symmetry type Lattice constants A Density g cm3a b cAcF3 White Hexagonal LaF3 4 27 7 53 7 88PaF4 Dark brown Monoclinic 12 7 10 7 8 42 PaF5 Black Tetragonal b UF5 11 53 5 19 ThF4 Colorless Monoclinic 13 10 99 8 58 5 71UF3 Reddish purple Hexagonal 7 18 7 34 8 54UF4 Green Monoclinic 11 27 10 75 8 40 6 72a UF5 Bluish Tetragonal 6 52 4 47 5 81b UF5 Bluish Tetragonal 11 47 5 20 6 45UF6 Yellowish Orthorhombic 9 92 8 95 5 19 5 06NpF3 Black or purple Hexagonal 7 129 7 288 9 12NpF4 Light green Monoclinic 12 67 10 62 8 41 6 8NpF6 Orange Orthorhombic 9 91 8 97 5 21 5PuF3 Violet blue Trigonal 7 09 7 25 9 32PuF4 Pale brown Monoclinic 12 59 10 57 8 28 6 96PuF6 Red brown Orthorhombic 9 95 9 02 3 26 4 86AmF3 Pink or light beige hexagonal LaF3 7 04 75 106 7 255 9 53AmF4 Orange red Monoclinic 12 53 10 51 8 20 CmF3 From brown to white Hexagonal 4 041 7 179 9 7CmF4 Yellow Monoclinic UF4 12 51 10 51 8 20 BkF3 Yellow green Trigonal LaF3 Orthorhombic YF3 6 97 6 7 7 09 7 14 4 41 10 15 9 7BkF4 Monoclinic UF4 12 47 10 58 8 17 CfF3 Trigonal LaF3 Orthorhombic YF3 6 94 6 65 7 04 7 10 4 39 CfF4 Monoclinic UF4 Monoclinic UF4 1 242 1 233 1 047 1 040 8 126 8 113 nbsp Einsteinium triiodide glowing in the darkActinides easily react with halogens forming salts with the formulas MX3 and MX4 X halogen So the first berkelium compound BkCl3 was synthesized in 1962 with an amount of 3 nanograms Like the halogens of rare earth elements actinide chlorides bromides and iodides are water soluble and fluorides are insoluble Uranium easily yields a colorless hexafluoride which sublimates at a temperature of 56 5 C because of its volatility it is used in the separation of uranium isotopes with gas centrifuge or gaseous diffusion Actinide hexafluorides have properties close to anhydrides They are very sensitive to moisture and hydrolyze forming AnO2F2 107 The pentachloride and black hexachloride of uranium were synthesized but they are both unstable 91 Action of acids on actinides yields salts and if the acids are non oxidizing then the actinide in the salt is in low valence state U 2 H2SO4 U SO4 2 2 H2 2 Pu 6 HCl 2 PuCl3 3 H2However in these reactions the regenerating hydrogen can react with the metal forming the corresponding hydride Uranium reacts with acids and water much more easily than thorium 91 Actinide salts can also be obtained by dissolving the corresponding hydroxides in acids Nitrates chlorides sulfates and perchlorates of actinides are water soluble When crystallizing from aqueous solutions these salts forming a hydrates such as Th NO3 4 6H2O Th SO4 2 9H2O and Pu2 SO4 3 7H2O Salts of high valence actinides easily hydrolyze So colorless sulfate chloride perchlorate and nitrate of thorium transform into basic salts with formulas Th OH 2SO4 and Th OH 3NO3 The solubility and insolubility of trivalent and tetravalent actinides is like that of lanthanide salts So phosphates fluorides oxalates iodates and carbonates of actinides are weakly soluble in water they precipitate as hydrates such as ThF4 3H2O and Th CrO4 2 3H2O 91 Actinides with oxidation state 6 except for the AnO22 type cations form AnO4 2 An2O7 2 and other complex anions For example uranium neptunium and plutonium form salts of the Na2UO4 uranate and NH4 2U2O7 diuranate types In comparison with lanthanides actinides more easily form coordination compounds and this ability increases with the actinide valence Trivalent actinides do not form fluoride coordination compounds whereas tetravalent thorium forms K2ThF6 KThF5 and even K5ThF9 complexes Thorium also forms the corresponding sulfates for example Na2SO4 Th SO4 2 5H2O nitrates and thiocyanates Salts with the general formula An2Th NO3 6 nH2O are of coordination nature with the coordination number of thorium equal to 12 Even easier is to produce complex salts of pentavalent and hexavalent actinides The most stable coordination compounds of actinides tetravalent thorium and uranium are obtained in reactions with diketones e g acetylacetone 91 Applications Edit nbsp Interior of a smoke detector containing americium 241 While actinides have some established daily life applications such as in smoke detectors americium 108 109 and gas mantles thorium 79 they are mostly used in nuclear weapons and as fuel in nuclear reactors 79 The last two areas exploit the property of actinides to release enormous energy in nuclear reactions which under certain conditions may become self sustaining chain reactions nbsp Self illumination of a nuclear reactor by Cherenkov radiation The most important isotope for nuclear power applications is uranium 235 It is used in the thermal reactor and its concentration in natural uranium does not exceed 0 72 This isotope strongly absorbs thermal neutrons releasing much energy One fission act of 1 gram of 235U converts into about 1 MW day Of importance is that 23592 U emits more neutrons than it absorbs 110 upon reaching the critical mass 23592 U enters into a self sustaining chain reaction 73 Typically uranium nucleus is divided into two fragments with the release of 2 3 neutrons for example 23592 U 10 n 11545 Rh 11847 Ag 310 nOther promising actinide isotopes for nuclear power are thorium 232 and its product from the thorium fuel cycle uranium 233 Nuclear reactor 73 111 112 The core of most Generation II nuclear reactors contains a set of hollow metal rods usually made of zirconium alloys filled with solid nuclear fuel pellets mostly oxide carbide nitride or monosulfide of uranium plutonium or thorium or their mixture the so called MOX fuel The most common fuel is oxide of uranium 235 nbsp Nuclear reactor schemeFast neutrons are slowed by moderators which contain water carbon deuterium or beryllium as thermal neutrons to increase the efficiency of their interaction with uranium 235 The rate of nuclear reaction is controlled by introducing additional rods made of boron or cadmium or a liquid absorbent usually boric acid Reactors for plutonium production are called breeder reactor or breeders they have a different design and use fast neutrons Emission of neutrons during the fission of uranium is important not only for maintaining the nuclear chain reaction but also for the synthesis of the heavier actinides Uranium 239 converts via b decay into plutonium 239 which like uranium 235 is capable of spontaneous fission The world s first nuclear reactors were built not for energy but for producing plutonium 239 for nuclear weapons About half of the produced thorium is used as the light emitting material of gas mantles 79 Thorium is also added into multicomponent alloys of magnesium and zinc So the Mg Th alloys are light and strong but also have high melting point and ductility and thus are widely used in the aviation industry and in the production of missiles Thorium also has good electron emission properties with long lifetime and low potential barrier for the emission 110 The relative content of thorium and uranium isotopes is widely used to estimate the age of various objects including stars see radiometric dating 113 The major application of plutonium has been in nuclear weapons where the isotope plutonium 239 was a key component due to its ease of fission and availability Plutonium based designs allow reducing the critical mass to about a third of that for uranium 235 114 The Fat Man type plutonium bombs produced during the Manhattan Project used explosive compression of plutonium to obtain significantly higher densities than normal combined with a central neutron source to begin the reaction and increase efficiency Thus only 6 2 kg of plutonium was needed for an explosive yield equivalent to 20 kilotons of TNT 115 See also Nuclear weapon design Hypothetically as little as 4 kg of plutonium and maybe even less could be used to make a single atomic bomb using very sophisticated assembly designs 116 Plutonium 238 is potentially more efficient isotope for nuclear reactors since it has smaller critical mass than uranium 235 but it continues to release much thermal energy 0 56 W g 109 117 by decay even when the fission chain reaction is stopped by control rods Its application is limited by its high price about US 1000 g This isotope has been used in thermopiles and water distillation systems of some space satellites and stations So Galileo and Apollo spacecraft e g Apollo 14 118 had heaters powered by kilogram quantities of plutonium 238 oxide this heat is also transformed into electricity with thermopiles The decay of plutonium 238 produces relatively harmless alpha particles and is not accompanied by gamma irradiation Therefore this isotope 160 mg is used as the energy source in heart pacemakers where it lasts about 5 times longer than conventional batteries 109 Actinium 227 is used as a neutron source Its high specific energy 14 5 W g and the possibility of obtaining significant quantities of thermally stable compounds are attractive for use in long lasting thermoelectric generators for remote use 228Ac is used as an indicator of radioactivity in chemical research as it emits high energy electrons 2 18 MeV that can be easily detected 228Ac 228Ra mixtures are widely used as an intense gamma source in industry and medicine 30 Development of self glowing actinide doped materials with durable crystalline matrices is a new area of actinide utilization as the addition of alpha emitting radionuclides to some glasses and crystals may confer luminescence 119 Toxicity Edit nbsp Schematic illustration of penetration of radiation through sheets of paper aluminium and lead brick nbsp Periodic table with elements colored according to the half life of their most stable isotope Elements which contain at least one stable isotope Slightly radioactive elements the most stable isotope is very long lived with a half life of over two million years Significantly radioactive elements the most stable isotope has half life between 800 and 34 000 years Radioactive elements the most stable isotope has half life between one day and 130 years Highly radioactive elements the most stable isotope has half life between several minutes and one day Extremely radioactive elements the most stable known isotope has half life less than several minutes Radioactive substances can harm human health via i local skin contamination ii internal exposure due to ingestion of radioactive isotopes and iii external overexposure by b activity and g radiation Together with radium and transuranium elements actinium is one of the most dangerous radioactive poisons with high specific a activity The most important feature of actinium is its ability to accumulate and remain in the surface layer of skeletons At the initial stage of poisoning actinium accumulates in the liver Another danger of actinium is that it undergoes radioactive decay faster than being excreted Adsorption from the digestive tract is much smaller 0 05 for actinium than radium 30 Protactinium in the body tends to accumulate in the kidneys and bones The maximum safe dose of protactinium in the human body is 0 03 µCi that corresponds to 0 5 micrograms of 231Pa This isotope which might be present in the air as aerosol is 2 5 108 times more toxic than hydrocyanic acid 61 contradictory Plutonium when entering the body through air food or blood e g a wound mostly settles in the lungs liver and bones with only about 10 going to other organs and remains there for decades The long residence time of plutonium in the body is partly explained by its poor solubility in water Some isotopes of plutonium emit ionizing a radiation which damages the surrounding cells The median lethal dose LD50 for 30 days in dogs after intravenous injection of plutonium is 0 32 milligram per kg of body mass and thus the lethal dose for humans is approximately 22 mg for a person weighing 70 kg the amount for respiratory exposure should be approximately four times greater Another estimate assumes that plutonium is 50 times less toxic than radium and thus permissible content of plutonium in the body should be 5 µg or 0 3 µCi Such amount is nearly invisible under microscope After trials on animals this maximum permissible dose was reduced to 0 65 µg or 0 04 µCi Studies on animals also revealed that the most dangerous plutonium exposure route is through inhalation after which 5 25 of inhaled substances is retained in the body Depending on the particle size and solubility of the plutonium compounds plutonium is localized either in the lungs or in the lymphatic system or is absorbed in the blood and then transported to the liver and bones Contamination via food is the least likely way In this case only about 0 05 of soluble 0 01 insoluble compounds of plutonium absorbs into blood and the rest is excreted Exposure of damaged skin to plutonium would retain nearly 100 of it 93 Using actinides in nuclear fuel sealed radioactive sources or advanced materials such as self glowing crystals has many potential benefits However a serious concern is the extremely high radiotoxicity of actinides and their migration in the environment 120 Use of chemically unstable forms of actinides in MOX and sealed radioactive sources is not appropriate by modern safety standards There is a challenge to develop stable and durable actinide bearing materials which provide safe storage use and final disposal A key need is application of actinide solid solutions in durable crystalline host phases 119 Nuclear properties EditHalf lives and branching fractions for actinides and natural decay products 121 Nuclide Half life Decay mode Branching fraction Source20681 Tl 4 202 0 011 m b 1 0 LNHB20881 Tl 3 060 0 008 m b 1 0 BIPM 521082 Pb 22 20 0 22 y b 1 0 ENSDFa 1 9 0 4 x 10 821182 Pb 36 1 0 2 m b 1 0 ENSDF21282 Pb 10 64 0 01 h b 1 0 BIPM 521482 Pb 26 8 0 9 m b 1 0 ENSDF21183 Bi 2 14 0 02 m b 0 00276 0 00004 ENSDFa 0 99724 0 0000421283 Bi 60 54 0 06 m a 0 3593 0 0007 BIPM 5b 0 6407 0 000721483 Bi 19 9 0 4 m a 0 00021 0 00001 ENSDFb 0 99979 0 0000121084 Po 138 376 0 002 d a 1 0 ENSDF21986 Rn 3 96 0 01 s a 1 0 ENSDF22086 Rn 55 8 0 3 s a 1 0 BIPM 522187 Fr 4 9 0 2 m b 0 00005 0 00003 ENSDFa 0 99995 0 0000322388 Ra 11 43 0 05 d a 1 0 ENSDF14C 8 9 0 4 x 10 1022488 Ra 3 627 0 007 d a 1 0 BIPM 522588 Ra 14 9 0 2 d b 1 0 ENSDF22688 Ra 1 600 0 007 x 103 y a 1 0 BIPM 522888 Ra 5 75 0 03 y b 1 0 ENSDF22489 Ac 2 78 0 17 h a 0 091 0 020 0 014 ENSDFEC 0 909 0 014 0 02022589 Ac 10 0 0 1 d a 1 0 ENSDF22789 Ac 21 772 0 003 y a 0 01380 0 00004 ENSDFb 0 98620 0 0000422889 Ac 6 15 0 02 h b 1 0 ENSDF22790 Th 18 718 0 005 d a 1 0 BIPM 522890 Th 698 60 0 23 d a 1 0 BIPM 522990 Th 7 34 0 16 x 103 y a 1 0 ENSDF23090 Th 7 538 0 030 x 104 y a 1 0 ENSDFSF 4 x 10 1323190 Th 25 52 0 01 h b 1 0 ENSDFa 4 x 10 1323290 Th 1 405 0 006 x 1010 y a 1 0 ENSDFSF 1 1 0 4 x 10 1123390 Th 22 15 0 15 m b 1 0 LNHB23490 Th 24 10 0 03 d b 1 0 ENSDF23191 Pa 3 276 0 011 x 104 y a 1 0 ENSDFSF 3 x 10 1223291 Pa 1 32 0 02 d EC 0 00003 0 00001 ENSDFb 0 99997 0 0000123391 Pa 26 98 0 02 d b 1 0 LNHB23491 Pa 6 70 0 05 h b 1 0 ENSDF234m91 Pa 1 159 0 016 m IT 0 0016 0 0002 IAEA CRP XGb 0 9984 0 000223292 U 68 9 0 4 y a 1 0 ENSDFSF23392 U 1 592 0 002 x 105 y a 1 0 ENSDFSF23492 U 2 455 0 006 x 105 y a 1 0 LNHBSF 1 6 0 2 x 10 11235m92 U 26 1 m IT 1 0 ENSDF23592 U 7 038 0 005 x 108 y a 1 0 ENSDFSF 7 2 x 10 1123692 U 2 342 0 004 x 107 y a 1 0 ENSDFSF 9 4 0 4 x 10 1023792 U 6 749 0 016 d b 1 0 LNHB23892 U 4 468 0 005 x 109 y a 1 0 LNHBSF 5 45 0 04 x 10 723992 U 23 45 0 02 m b 1 0 ENSDF23693 Np 1 55 0 08 x 105 y a 0 0016 0 0006 LNHBb 0 120 0 006EC 0 878 0 006236m93 Np 22 5 0 4 h b 0 47 0 01 LNHBEC 0 53 0 0123793 Np 2 144 0 007 x 106 y a 1 0 ENSDFSF23893 Np 2 117 0 002 d b 1 0 ENSDF23993 Np 2 356 0 003 d b 1 0 ENSDF23694 Pu 2 858 0 008 y a 1 0 ENSDFReferences LNHB Laboratoire National Henri Becquerel Recommended Data http www nucleide org DDEP WG DDEPdata htm Archived 13 February 2021 at the Wayback Machine 3 October 2006 BIPM 5 M M Be V Chiste C Dulieu E Browne V Chechev N Kuzmenko R Helmer A Nichols E Schonfeld R Dersch Monographie BIPM 5 Table of Radionuclides Vol 2 A 151 to 242 2004 ENSDF Evaluated Nuclear Structure Data File Brookhaven National Laboratory Retrieved 15 November 2006 IAEA CRP XG M M Be V P Chechev R Dersch O A M Helene R G Helmer M Herman S Hlavac A Marcinkowski G L Molnar A L Nichols E Schonfeld V R Vanin M J Woods IAEA CRP Update of X Ray and Gamma Ray Decay Data Standards for Detector Calibration and Other Applications IAEA Scientific and Technical Information report STI PUB 1287 May 2007 International Atomic Energy Agency Vienna Austria ISBN 92 0 113606 4 See also EditActinides in the environment Lanthanides Major actinides Minor actinides TransuranicsNotes Edit Nobelium and lawrencium were almost simultaneously discovered by Soviet and American scientists Specific activity is calculated by given in the table half lives and the probability of spontaneous fissionReferences Edit a b c Theodore Gray 2009 The Elements A Visual Exploration of Every Known Atom in the Universe New York Black Dog amp Leventhal Publishers p 240 ISBN 978 1 57912 814 2 Morss Lester Asprey Larned B 1 August 2018 Actinoid element britannica com Encyclopaedia Britannica Retrieved 3 September 2020 Neil G Connelly et al 2005 Elements Nomenclature of Inorganic Chemistry London Royal Society of Chemistry p 52 ISBN 978 0 85404 438 2 Greenwood Norman N Earnshaw Alan 1997 Chemistry of the Elements 2nd ed Butterworth Heinemann pp 1230 1242 ISBN 978 0 08 037941 8 Jensen William B 2015 The positions of lanthanum actinium and lutetium lawrencium in the periodic table an update Foundations of Chemistry 17 23 31 doi 10 1007 s10698 015 9216 1 S2CID 98624395 Retrieved 28 January 2021 Scerri Eric 18 January 2021 Provisional Report on Discussions on Group 3 of the Periodic Table Chemistry International 43 1 31 34 doi 10 1515 ci 2021 0115 S2CID 231694898 Neve Francesco 2022 Chemistry of superheavy transition metals Journal of Coordination Chemistry 75 17 18 2287 2307 doi 10 1080 00958972 2022 2084394 S2CID 254097024 a b c Greenwood p 1250 a b Fields P Studier M Diamond H Mech J Inghram M Pyle G Stevens C Fried S Manning W et al 1956 Transplutonium Elements in Thermonuclear Test Debris Physical Review 102 1 180 182 Bibcode 1956PhRv 102 180F doi 10 1103 PhysRev 102 180 a b c Greenwood p 1252 Myasoedov p 7 E Fermi 1934 Possible Production of Elements of Atomic Number Higher than 92 Nature 133 3372 898 899 Bibcode 1934Natur 133 898F doi 10 1038 133898a0 Mehra Jagdish Rechenberg Helmut 2001 The historical development of quantum theory Springer p 966 ISBN 978 0 387 95086 0 Seaborg G T 1994 118 Origin of the actinide concept In K A Gschneidner Jr L Eyring G R Choppin G H Landet eds Handbook on the Physics and Chemistry of Rare Earths Vol 18 Lanthanides Actinides Chemistry Elsevier pp 4 6 10 14 Wallmann J C 1959 The first isolations of the transuranium elements A historical survey Journal of Chemical Education 36 7 340 Bibcode 1959JChEd 36 340W doi 10 1021 ed036p340 Myasoedov p 9 Myasoedov p 14 Martin Heinrich Klaproth 1789 Chemische Untersuchung des Uranits einer neuentdeckten metallischen Substanz Chemische Annalen 2 387 403 E M Peligot 1842 Recherches Sur L Uranium Annales de chimie et de physique 5 5 5 47 Ingmar Grenthe 2006 Uranium The Chemistry of the Actinide and Transactinide Elements pp 253 698 doi 10 1007 1 4020 3598 5 5 ISBN 978 1 4020 3555 5 K Zimmerman Ann 213 290 1882 216 1 1883 Ber 15 1882 849 Golub p 214 Berzelius J J 1829 Untersuchung eines neues Minerals und einer darin erhalten zuvor unbekannten Erde Investigation of a new mineral and of a previously unknown earth contained therein Annalen der Physik und Chemie 16 7 385 415 Bibcode 1829AnP 92 385B doi 10 1002 andp 18290920702 modern citation Annalen der Physik vol 92 no 7 pp 385 415 Berzelius J J 1829 Undersokning af ett nytt mineral Thorit som innehaller en forut obekant jord Investigation of a new mineral thorite as contained in a previously unknown earth PDF Kungliga Svenska Vetenskaps Akademiens Handlingar Transactions of the Royal Swedish Science Academy 1 30 Archived PDF from the original on 9 October 2022 Andre Louis Debierne 1899 Sur un nouvelle matiere radio active Comptes Rendus in French 129 593 595 Andre Louis Debierne 1900 1901 Sur un nouvelle matiere radio actif l actinium Comptes Rendus in French 130 906 908 H W Kirby 1971 The Discovery of Actinium Isis 62 3 290 308 doi 10 1086 350760 JSTOR 229943 S2CID 144651011 J P Adloff 2000 The centenary of a controversial discovery actinium Radiochim Acta 88 3 4 2000 123 128 doi 10 1524 ract 2000 88 3 4 123 S2CID 94016074 Golub p 213 a b c d e f g h i j Z K Karalova B Myasoedov 1982 Actinium Analytical chemistry items Moscow Nauka Hakala Reino W 1952 Letters Journal of Chemical Education 29 11 581 Bibcode 1952JChEd 29 581H doi 10 1021 ed029p581 2 George B Kauffman 1997 Victor Moritz Goldschmidt 1888 1947 A Tribute to the Founder of Modern Geochemistry on the Fiftieth Anniversary of His Death The Chemical Educator 2 5 1 26 doi 10 1007 s00897970143a S2CID 101664962 John Emsley 2001 Protactinium Nature s Building Blocks An A Z Guide to the Elements Oxford England Oxford University Press pp 347 349 ISBN 978 0 19 850340 8 a b K Fajans O Gohring 1913 Uber die komplexe Natur des Ur X Naturwissenschaften 1 14 339 Bibcode 1913NW 1 339F doi 10 1007 BF01495360 S2CID 40667401 K Fajans O Gohring 1913 Uber das Uran X2 das neue Element der Uranreihe Physikalische Zeitschrift 14 877 84 a b Greenwood p 1251 Edwin McMillan Abelson Philip 1940 Radioactive Element 93 Physical Review 57 12 1185 1186 Bibcode 1940PhRv 57 1185M doi 10 1103 PhysRev 57 1185 2 a b c d e f V A Mikhailov ed 1971 Analytical chemistry of neptunium Moscow Nauka Hanford Cultural Resources Program US Department of Energy 2002 Hanford Site Historic District History of the Plutonium Production Facilities 1943 1990 Columbus OH Battelle Press pp 1 22 1 27 doi 10 2172 807939 ISBN 978 1 57477 133 6 Nina Hall 2000 The New Chemistry A Showcase for Modern Chemistry and Its Applications Cambridge University Press pp 8 9 ISBN 978 0 521 45224 3 Myasoedov p 8 Thompson S G Ghiorso A Seaborg G T 1950 Element 97 Phys Rev 77 6 838 839 Bibcode 1950PhRv 77 838T doi 10 1103 PhysRev 77 838 2 Thompson S G Ghiorso A Seaborg G T 1950 The New Element Berkelium Atomic Number 97 Phys Rev 80 5 781 789 Bibcode 1950PhRv 80 781T doi 10 1103 PhysRev 80 781 Wallace W Schulz 1976 The Chemistry of Americium U S Department of Commerce p 1 Thompson S Ghiorso A Seaborg G 1950 Element 97 Physical Review 77 6 838 839 Bibcode 1950PhRv 77 838T doi 10 1103 PhysRev 77 838 2 Thompson S Ghiorso A Seaborg G 1950 The New Element Berkelium Atomic Number 97 Physical Review 80 5 781 789 Bibcode 1950PhRv 80 781T doi 10 1103 PhysRev 80 781 S G Thompson K Street Jr A Ghiorso G T Seaborg 1950 Element 98 Physical Review 78 3 298 299 Bibcode 1950PhRv 78 298T doi 10 1103 PhysRev 78 298 2 S G Thompson K Street Jr A Ghiorso G T Seaborg 1950 The New Element Californium Atomic Number 98 PDF Physical Review 80 5 790 796 Bibcode 1950PhRv 80 790T doi 10 1103 PhysRev 80 790 Archived PDF from the original on 9 October 2022 K Street Jr S G Thompson G T Seaborg 1950 Chemical Properties of Californium J Am Chem Soc 72 10 4832 4835 doi 10 1021 ja01166a528 hdl 2027 mdp 39015086449173 Archived from the original on 15 May 2016 Retrieved 23 October 2010 S G Thompson and B B Cunningham 1958 First Macroscopic Observations of the Chemical Properties of Berkelium and Californium supplement to Paper P 825 presented at the Second Intl Conf Peaceful Uses Atomic Energy Geneva Darleane C Hoffman Albert Ghiorso Glenn Theodore Seaborg 2000 The transuranium people the inside story Imperial College Press ISBN 1 86094 087 0 pp 141 142 a b A Ghiorso S G Thompson G H Higgins G T Seaborg M H Studier P R Fields S M Fried H Diamond J F Mech G L Pyle J R Huizenga A Hirsch W M Manning C I Browne H L Smith R W Spence 1955 New Elements Einsteinium and Fermium Atomic Numbers 99 and 100 Phys Rev 99 3 1048 1049 Bibcode 1955PhRv 99 1048G doi 10 1103 PhysRev 99 1048 S Thompson A Ghiorso B G Harvey G R Choppin 1954 Transcurium Isotopes Produced in the Neutron Irradiation of Plutonium Physical Review 93 4 908 Bibcode 1954PhRv 93 908T doi 10 1103 PhysRev 93 908 G R Choppin S G Thompson A Ghiorso B G Harvey 1954 Nuclear Properties of Some Isotopes of Californium Elements 99 and 100 Physical Review 94 4 1080 1081 Bibcode 1954PhRv 94 1080C doi 10 1103 PhysRev 94 1080 Albert Ghiorso 2003 Einsteinium and Fermium Chemical and Engineering News 81 36 A Ghiorso B Harvey G Choppin S Thompson G Seaborg 1955 New Element Mendelevium Atomic Number 101 pp 1518 1519 Bibcode 1955PhRv 98 1518G doi 10 1103 PhysRev 98 1518 ISBN 978 981 02 1440 1 a href Template Cite book html title Template Cite book cite book a journal ignored help a b c d e f g h Audi G Kondev F G Wang M Huang W J Naimi S 2017 The NUBASE2016 evaluation of nuclear properties PDF Chinese Physics C 41 3 030001 Bibcode 2017ChPhC 41c0001A doi 10 1088 1674 1137 41 3 030001 a b c d e f g h i j Table of nuclides IAEA Retrieved 7 July 2010 Myasoedov pp 19 21 a b Greenwood p 1254 a b c d e f g E S Palshin 1968 Analytical chemistry of protactinium Moscow Nauka I P Alimarin 1962 A P Vinogradov ed Analytical chemistry of uranium Moscow Publisher USSR Academy of Sciences Kondev F G Wang M Huang W J Naimi S Audi G 2021 The NUBASE2020 evaluation of nuclear properties PDF Chinese Physics C 45 3 030001 doi 10 1088 1674 1137 abddae a b Myasoedov p 18 a b c Myasoedov p 22 Myasoedov p 25 Table of elements compounds isotopes in Russian Archived from the original on 12 July 2010 Retrieved 7 July 2010 Standard Atomic Weights 2013 Commission on Isotopic Abundances and Atomic Weights Soppera N Bossant M Dupont E 2014 JANIS 4 An Improved Version of the NEA Java based Nuclear Data Information System Nuclear Data Sheets Elsevier BV 120 294 296 Bibcode 2014NDS 120 294S doi 10 1016 j nds 2014 07 071 Matthew W Francis et al 2014 Reactor fuel isotopics and code validation for nuclear applications ORNL TM 2014 464 Oak Ridge Tennessee p 11 Jay H Lehr Janet K Lehr 2000 Standard handbook of environmental science health and technology McGraw Hill Professional pp 2 38 ISBN 978 0 07 038309 8 Lide D R ed 2005 CRC Handbook of Chemistry and Physics 86th ed Boca Raton FL CRC Press ISBN 0 8493 0486 5 a b c d e f g h i Yu D Tretyakov ed 2007 Non organic chemistry in three volumes Chemistry of transition elements Vol 3 Moscow Academy ISBN 978 5 7695 2533 9 World Uranium Mining World Nuclear Association Archived from the original on 26 June 2010 Retrieved 11 June 2010 a b c F Weigel J Katz G Seaborg 1997 The Chemistry of the Actinide Elements Vol 2 Moscow Mir ISBN 978 5 03 001885 0 Thorium USGS Mineral Commodities a b c d e f g Golub pp 215 217 Greenwood pp 1255 1261 a b c d e Greenwood p 1255 A E van Arkel de Boer J H 1925 Darstellung von reinem Titanium Zirkonium Hafnium und Thoriummetall Zeitschrift fur Anorganische und Allgemeine Chemie in German 148 1 345 350 doi 10 1002 zaac 19251480133 I L Knunyants 1961 Short Chemical Encyclopedia Vol 1 Moscow Soviet Encyclopedia Golub pp 218 219 a b c Greenwood p 1263 a b John Emsley 2011 Nature s Building Blocks An A Z Guide to the Elements New ed New York NY Oxford University Press ISBN 978 0 19 960563 7 Peterson Ivars 7 December 1991 Uranium displays rare type of radioactivity Science News Archived from the original on 18 January 2012 Greenwood p 1265 Domanov V P Lobanov Yu V October 2011 Formation of volatile curium VI trioxide CmO3 Radiochemistry 53 5 453 456 doi 10 1134 S1066362211050018 ISSN 1066 3622 S2CID 98052484 a b Greenwood p 1264 General Properties and Reactions of the Actinides LibreTexts 22 May 2015 Many actinide metals hydrides carbides alloys and other compounds may ignite at room temperature in a finely divided state Myasoedov pp 30 31 a b c d e f g h i j k l Golub pp 222 227 Greenwood p 1278 a b B A Nadykto L F Timofeeva eds 2003 Plutonium Fundamental Problems Vol 1 Sarov VNIIEF ISBN 978 5 9515 0024 3 M S Milyukova 1965 Analytical chemistry of plutonium Moscow Nauka ISBN 978 0 250 39918 5 a b Myasoedov pp 25 29 Deblonde Gauthier J P Sturzbecher Hoehne Manuel Jong Wibe A de Brabec Jiri Corie Y Ralston Illy Marie Claire An Dahlia D Rupert Peter B Strong Roland K September 2017 Chelation and stabilization of berkelium in oxidation state IV Nature Chemistry 9 9 843 849 Bibcode 2017NatCh 9 843D doi 10 1038 nchem 2759 ISSN 1755 4349 OSTI 1436161 PMID 28837177 Myasoedov p 88 a b Tablica Inorganic and Coordination compounds in Russian Retrieved 11 July 2010 According to other sources cubic sesquioxide of curium is olive green See Soedineniya curium site XuMuK ru in Russian Archived from the original on 18 August 2010 Retrieved 11 July 2010 The atmosphere during the synthesis affects the lattice parameters which might be due to non stoichiometry as a result of oxidation or reduction of the trivalent californium Main form is the cubic oxide of californium III a b c Greenwood p 1268 L R Morss Norman M Edelstein Jean Fuger 2011 The Chemistry of the Actinide and Transactinide Elements Set Vol 1 6 Springer p 2139 ISBN 978 94 007 0210 3 a b Krivovichev Sergei Burns Peter Tananaev Ivan 2006 Chapter 3 Structural Chemistry of Inorganic Actinide Compounds Elsevier pp 67 78 ISBN 978 0 08 046791 7 a b Greenwood p 1270 Myasoedov pp 96 99 Nave S Haire R Huray Paul 1983 Magnetic properties of actinide elements having the 5f6 and 5f7 electronic configurations Physical Review B 28 5 2317 2327 Bibcode 1983PhRvB 28 2317N doi 10 1103 PhysRevB 28 2317 Greenwood p 1269 Smoke Detectors and Americium Nuclear Issues Briefing Paper 35 May 2002 a b c Greenwood p 1262 a b Golub pp 220 221 G G Bartolomei V D Baybakov M S Alkhutov G A Bach 1982 Basic theories and methods of calculation of nuclear reactors Moscow Energoatomizdat Greenwood pp 1256 1261 Sergey Popov Alexander Sergeev 2008 Universal Alchemy Vokrug Sveta in Russian 2811 4 David L Heiserman 1992 Element 94 Plutonium Exploring Chemical Elements and their Compounds New York TAB Books p 338 ISBN 978 0 8306 3018 9 John Malik September 1985 The Yields of the Hiroshima and Nagasaki Explosions PDF Los Alamos p Table VI LA 8819 Archived PDF from the original on 24 February 2009 Retrieved 15 February 2009 Nuclear Weapon Design Federation of American Scientists 1998 Archived from the original on 26 December 2008 Retrieved 7 December 2008 John Holdren and Matthew Bunn Nuclear Weapons Design amp Materials Project on Managing the Atom MTA for NTI 25 November 2002 Apollo 14 Press Kit 01 11 71 NASA pp 38 39 a b B E Burakov M I Ojovan W E Lee 2010 Crystalline Materials for Actinide Immobilisation World Scientific ISBN 978 1 84816 418 5 M I Ojovan W E Lee 2005 An Introduction to Nuclear Waste Immobilisation Amsterdam Elsevier ISBN 978 0 08 044462 8 Half lives and branching fractions for actinides and natural decay products www nds iaea org IAEA Retrieved 29 September 2018 Bibliography EditGolub A M 1971 Obshaya i neorganicheskaya himiya General and Inorganic Chemistry Vol 2 Greenwood Norman N Earnshaw Alan 1997 Chemistry of the Elements 2nd ed Butterworth Heinemann ISBN 978 0 08 037941 8 Myasoedov B 1972 Analytical chemistry of transplutonium elements Moscow Nauka ISBN 978 0 470 62715 0 External links Edit nbsp Wikimedia Commons has media related to Actinides Lawrence Berkeley Laboratory image of historic periodic table by Seaborg showing actinide series for the first time Lawrence Livermore National Laboratory Uncovering the Secrets of the Actinides Los Alamos National Laboratory Actinide Research Quarterly Retrieved from https en wikipedia org w index php title Actinide amp oldid 1176193030, wikipedia, wiki, book, books, library,

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